mew225

8/10/2019 mew225

http://slidepdf.com/reader/full/mew225 1/67

N o . 2 2 5

FEBRUARY 2015

THE ESSENTIAL MAGAZINE FOR EVERY HOBBY ENGINEER

£ 4 .2 0

ENGINEERING GROUP

C O VER FE A TUR E

Join the conversation about this issue: www.model-engineer.co.uk

POWER FEEDFor a MyfordSuper 7 Lathe

MINIATURE INTERNAL COMBUSTION ENGINES BOOK

FREE FOR ALL NEW UK SUBSCRIBERS(UK Print + Digital &

Print Subscribers only)

Ball Turningon a Mini Lathe

T ools at t he M odelE ng ineer E x hibit ion

w w w . h o b b y m a g a z i n e s . o r g

http://www.hobbymagazines.org/


8/10/2019 mew225

http://slidepdf.com/reader/full/mew225 2/67 www.emcomachinetools.co.uk

We regularly ship worldwide Please contact us for stock levels and more technical detail

MORE MACHINES AND ACCESSORIES ON LINE

PRO Machine Tools Ltd.

17 Station Road Business Park, Barnack,Stamford, Lincolnshire PE9 3DW

tel: 01780 740956 • fax: 01780 740957

email: [email protected]

Our machines suit the discerning hobbyist as well as blue chip industry

Wabeco produce quality rather than eastern quantity

CNC machines are offered with a varietyof CNC control and software systems,and still be used as manual machines.

Wabeco produce precisionmade machines by rigorous quality

control and accuracy testing.

Wabeco LatheD4000E

•Centre Distance – 350mm

•Centre Height – 100mm

•Speed – 30 to 2300rpm

•Power – 1.4 KW

•Size – 860 x 400 x 380mm

•Weight – 71kg

All of our prices can be found on our web site:

t aCNC

ofand

ma

WabecoCNC Lathe CC-D6000E

•Centre Distance –

600mm



•

Power – 1.4 KW

•Size – 1215 x

500 x 605mm

•Weight – 150Kg

•NCCAD/

NCCAD Pro

Wabeco Lathe D6000E•Centre Distance – 600 mm



•Power – 1.4 KW•Size – 1230 x 500 x 470mm

•Weight – 150kg

On ALL WABECO Machines warrantywarr 5year

warrantywarr 5year

warrantywarr 5year

warrantywarr 5year

Precision machines made in Germany for the discerning engineer!

ngineer!

WabecoMill

F1210E

• Table – 700 x 180mm

•Z axis – 280 mm


•Power – 1.4 KW

•Size – 900 x 610 x 960mm

•Weight – 101Kg

warrantywarr 5year

•

Table – 700 x 180mm •Z axis – 280mm •Speed –

140 to 3000rpm

•Power – 1.4 KW

•Size – 950

x 600 x 950mm

•Weight – 122Kg

•

NCCAD/NCCAD Pro

Wabeco

CNC MillCC-F1410E

warrantywarr

5

year

All lathes and mills are backed by anextensive range of tools and accessories




8/10/2019 mew225


3February 2015

On the Editor'sBench

Published by MyTimeMedia Ltd.Enterprise House, Enterprise Way,

Edenbridge, Kent TN8 6HFTel: 0844 412 2262

From outside UK: +44 (0)1689 869840www.model-engineer.co.uk

SUBSCRIPTIONSUK - New, Renewals & Enquiries

Tel: +44(0)1858 438798Email: [email protected]

USA & CANADA - New, Renewals & EnquiriesTel: (001)-866-647-9191

REST OF WORLD - New, Renewals & EnquiriesTel: +44 (0)1689 869896

Email: [email protected]

BACK ISSUES & BINDERSTel: 0844 848 8822

From outside UK: +44 2476 322234Email: [email protected]

Website: www.myhobbystore.co.uk

MODEL ENGINEERING PLANSTel: 0844 848 8822

From outside UK: +44 2476 322234Website: www.myhobbystore.co.uk/me-plans

EDITORIAL Editor: Neil Wyatt

Tel: +44 (0)1689 869 912Email: [email protected]

PRODUCTION

Design Manager: Siobhan NolanDesigner: Yvette Green

Illustrator: Grahame ChambersRetouching: Brian Vickers

Ad Production: Robin Gray

ADVERTISING Display and Classified Sales: Duncan Armstrong

Email: [email protected]

Tel: 0844 848 5238Online Sales: Ben Rayment

Email: [email protected] Tel: 0844 848 5240

MARKETING & SUBSCRIPTIONSSubscription Manager:

Kate Hall

MANAGEMENTHead of Design & Production: Julie MillerGroup Sales Manager: Duncan Armstrong

Chief Executive: Owen DaviesChairman: Peter Harkness

© MyTimeMedia Ltd. 2015 All rights reserved ISSN 0959-6909

The Publisher’s written consent must be obtained before any part of thispublication may be reproduced in any form whatsoever, including photocopiers,and information retrieval systems. All reasonable care is taken in the preparationof the magazine contents, but the publishers cannot be held legally responsiblefor errors in the contents of this magazine or for any loss however arising from

such errors, including loss resulting from negligence of our staff. Reliance placedupon the contents of this magazine is at reader’s own risk.

Model Engineers’ Workshop, ISSN 0959-6909, is published monthly withan additional issue in August by MYTIMEMEDIA Ltd, Enterprise House,

Enterprise Way, Edenbridge, Kent TN8 6HF, UK. The US annual subscriptionprice is 52.95GBP (equivalent to approximately 88USD). Airfreight and mailingin the USA by agent named Air Business Ltd, c/o Worldnet Shipping Inc., 156-15, 146th Avenue, 2nd Floor, Jamaica, NY 11434, USA. Periodicals postagepaid at Jamaica NY 11431. US Postmaster: Send address changes to Model

Engineers’ Workshop, Worldnet Shipping Inc., 156-15, 146th Avenue, 2nd Floor,Jamaica, NY 11434, USA. Subscription records are maintained at CDS GLOBALLtd, Tower House, Sovereign Park, Market Harborough, Leicester, LE16 9EF. Air

Business Ltd is acting as our mailing agent.

Many readers and users of the Model Engineerforum will be familiar with tangential tooling and theadvantages it offers. My interest was piqued by a fewfolk mentioning a very different tool which they also heldin high regard. I’ve been in touch with David Wimberleywho produces his own distinctive toolholder for medium-sized lathes. Like a tangential holder it has special angles tosimplify grinding, but it holds the toolbit nearly horizontal.Although more faces have to be ground, it potentially offersmore tool shapes than a tangential holder. As the relief onall ground faces is both the same and over a small area, it is not greatly moreinvolved to sharpen the tool. Because the tool is really for lathes of 4-inch centreheight and above, I’m having to make a special adaptor for my quick changetoolpost, but I will try out the tool over the next few weeks and report back.

WIMBERLEY TOOL HOLDER

Welcome to 2015As theaccompanyingpicture byM. Jacques Morelshows, there wereplenty of seasonalgood wishesexchanged on theModel Engineerweb forums. It’snow a good time to reflect on plans forthe next year. If you are like me, then

the past year has probably seen the listof projects grow, rather than shrink.Certainly taking up the reins of MEW has been a double edged sword forme, with more reason to be active inthe workshop, but probably less timethan ever to actually do things! In 2015,rather than trying to work through allmy unfinished projects - and failing tofinish any, I think I’ll focus on choosinga few ‘headline’ projects and try andpolish them off. Naturally one will bethe Super Adept lathe, but I will also aimto complete at least one engineeringmodel and a couple of electronic basedprojects. I think will also try and domore ‘short, sharp’ projects. Away fromspecific projects, I think my work couldbenefit from more effort spent on jigsand fixtures, as well as more attention totool and cutter sharpening. So, what areyou planning for the coming year?

New AuthorsI’d like to thank the readers whoresponded to my call for new authors inthe last issue. I have already received anumber of interesting offers of articleson topics which will help keep up thebreadth and variety of content MEW is known for. I should add that thisisn’t a purge of established authors

– the magazine needs a mixture of

experienced writers and fresh newideas. As always, email [email protected] letting me know ofany ideas you have for an article, or ifthere is anything you would particularlylike to see covered.

Model Engineer ExhibitionI greatly enjoyed the Model EngineerExhibition at Sandown, and was able tomeet many readers and contributors, aswell as many well-known faces in the

world of model engineering. Perhapsthis is one of the best parts of attendingthe show; you don’t just get to seepossibly the finest display of modelengineering anywhere in the world, butyou can meet the people behind thoseremarkable achievements and just howapproachable and ready to share theirthoughts and ideas they are.

Meet the MakersAt Sandown I was struck by the constantstream of visitors to the ‘Makers Area’. Itwas not a case of sceptical old engineerscoming to see what the youngsterswere doing with plastic and microchips– everywhere there was earnest andinspiring discussion of the possibilitiesoffered by fusing new technologieswith traditional skills. I commented toone chap exhibiting various embeddedmicrocontroller projects that the realrevolution will come when today’smakers become ‘empty nesters’ - whatsort of projects will they come upwith when they find they have someserious workshop time and resources?Some clues to the answer come fromthe SMEE Digital Workshop; with theirencouragement I have ordered somelaser-cut parts for a tiny Piccolo 3-axisCNC machine. More news on this cute

beginner’s project in a future issue.



8/10/2019 mew225


John Winter & Co. Ltd.

MAKE YOUR OWN CASTINGS

Model Engineering andSmall Scale

Foundry Work

• Crucibles • Ingots • Safety wear• Casting fluxes • Refractories,

thermal blankets & bricks• Oil bonded sands/sands/binders

• Sodium Silicates/Esters

Tel: Halifax +44(0)1422 364213Email: carol @ johnwinter.co.uk P.O. BOX 21 Washer Lane Works, Halifax HX2 7DP

Please take a look at our website:

www.johnwinter.co.uk

Apply toCarol White for a FREE

Catalogue/Price List

• •

••

• •

Hemingway Kits

126 Dunval Road, BridgnorthShropshire WV16 4LZUnited KingdomTel/Fax: +44 (0) 1746 767739Email:[email protected]

WorkshopAccessorykits

Hemingway

Hemingway Kitsprovide a range ofuniquely practicaltooling and challengingprojects for the smallworkshop owner.

Top Designers withproven designs

Laser print 3D CADdrawings with illustratedconstruction notes

Over 70 full materialkits to suit yourequipment

Fast, friendly andknowledgeable service

Send £2(refundable)for our latest

workshopcatalogue or visit

our websitewww.hemingwaykits.com



8/10/2019 mew225

http://slidepdf.com/reader/full/mew225 5/67 www.emcomachinetools.co.uk

We regularly ship worldwide Please contact us for stock levels and more technical detail

MORE MACHINES AND ACCESSORIES ON LINE

Our machines suit the discerning hobbyist as well as blue chip industry

All of our prices can be found on our web site:

Precision machines made in Italy for the discerning engineer!ineer!

PRO Machine Tools Ltd.

17 Station Road Business Park, Barnack,Stamford, Lincolnshire PE9 3DW

tel: 01780 740956 • fax: 01780 740957

email: [email protected]

ACCESSORIES

Lathe Chucks, Drill Chucks, TippedTools, Boring Bars, QCTP, HSS Tools,

End Mills, Slot Drills, Machine Vices,Clamping Sets, Slitting Saws, Arbors,

Boring Heads, Radius Mills, DROs,Rotary Table, CNC fits, Collet Chucks,

Collet Sets, Flanges, Face Mills,

Shell Mills and Much More...

All lathes and mills are backed by anextensive range of tools and accessories

d

Ceriani 400Series Mill

Ceriani 203 Lathe •Centre height - 100mm •Centre distance - 500mm •Swing over gap - 260mm •Spindle bore - 20 or 30mm •Motor - 1 HP •Weight - 80 Kgs

•Optional splash-back andsafetyguard

•Semi Norton gearbox •Four selectable feed rates plus screw cutting • Vari-speed option

•ISO30 Spindle• Table size - 580 x 150mm• Travel - 420 x 160 x 300mm

(XYZ)•1.5 KW Motor •100-3000 rpm vari-speed•Weight - 150 Kgs




8/10/2019 mew225


www.model-engineer.co.uk Model Engineers’ Workshop

Contents8 PARTING OFF IN

THE METAL LATHE Reg Merryweather has

designed an unusual

toolholder.

12 AN AINJESTHIGH SPEEDTHREADING UNIT

Andrew Johnston

recommissions an

interesting device.

17 HEAT TREATING O1and W1 STEELS

Richard Rex continues

his detailed look at

hardening steel.

24 BALL TURNING ONA MINI LATHE

Instead of buying an

accessory, Alastair Sinclair

decided to make use of the

his lathe’s rotating topslide

mount.

28 CHAIN DRILLINGMARKER JIG

Peter Wilton’s ‘made in

minutes’ device makes chain

drilling so much easier.

31 A POWEREDLEADSCREW FORA MYFORD LATHE

Rich Wightman and Julian

Harrison team up to make a

useful accessory.

36 THREADED INSERTSAND OTHERHOT TOPICS

When plastic meets metal,

these inserts offer a good

solution. Mark Noel tells

us how.

40 THE METALMASTER (IMPETUS)MACHINE TOOL

Mike Philpotts introduces an

unusual machine, with more

details on our website.

46 A PRECISIONMACHINE VICE

Morgan Jones describes life

with the Hobbymat MD65.

51 ONE MANAND HIS LATHE

Morgan Jones recounts life

with his Hobbymat MD65.

56 PRODUCING CADFILES FOR LASER ANDWATER JET CUTTING

Malcolm High outlines someof the pitfalls for those

needing laser cut parts.

58 WORKSHOP TOOLSAT THE MODELENGINEER EXHIBITION

The Editor reports back from

the exhibition at Sandown

in December.

63 BOOK REVIEW A review of Making Scale

Models by Mark Friend.

24

6

SUBSCRIBE TODAY! AND SAVE UP TO 23% OFF THE

SHOP PRICE PLUS RECEIVE A

FREE MINIATURE INTERNAL

COMBUSTION ENGINES BOOKWORTH £19.95

See page 45 for details.



8/10/2019 mew225


N o . 2 2 5

FEBRUARY 2015


£ 4 .2 0

ENGINEERINGGROUP

C O VER FEA TUR E

Jointheconversationabout thisissue: www.model-engineer.co.uk

POWER FEEDFor a MyfordSuper 7 Lathe

MINIATURE INTERNAL COMBUSTION ENGINES BOOK

FREE FOR ALL NEW UK SUBSCRIBERS(UKPrint+Digital&

PrintSubscribersonly)

Ball Turningon a Mini Lathe

T ools at t he M odel E ng ineer E x hibit ion

M 5 C o e r. i nd d 0 / 0 / 0 5 : 0

February 2015

Visit ourWebsite

for extra content andour online forum

The UrwickMetal MasterVisit www.model-

engineer.co.uk/metalmaster

to download a

comprehensive

document with

further details,

including dimensioned plans, of David Urwick’s

unconventional Metal Master machining centre,

featured in this issue.

FREE PLAN: A Spindle Moulder

A request from a forum member led to a digitalreprint of Norman A. Ough’s 1954 Model Engineer

article describing and detailing a miniature spindle

moulder. In effect, this is a dedicated machine to do

the same task as a table mounted router. A spindle

below a work table has shaped cutters pointing

upwards for profiling wood and the softer metals.

News from the 2014Model Engineer ExhibitionSee this report posted live while the exhibition was

taking place. The report features photos of models,

tools and all other aspects of the event.

Some of the other live topics on the forum include:

›Side Shields for Safety Glasses – what’s the most

cost effective way to protect your eyesight in the

workshop?

›The Warco WM250 Family – users of this popular

lathe compare notes and ideas.

›What did you do today (2015)? – A new thread

kicks off to share your workshop highlights of

2014, and your plans for 2015.Rich Wightman and Julian Harrisonput their electronic and machining

skills together to make a Super 7

power feed that is independent of

the change gear setup.

ON THE COVER ›››

Coming up...in the March issue

Inchanga recounts the ups and downs of twenty

years living with a far-Eastern milling machine,

Mike Haughton describes secure carriage locks

for the Myford Super 7 & Chester Craftsman

lathes, John Ashton fits a Quick Change Toolpost

to his Toolco 1130gv lathe and much more.

3 ON THE EDITOR’S BENCH The Editor’s commentary.

23 READERS’ TIPS Two new ideas for the workshop in our monthly

competition.

42 READERS’ FREE ADVERTS This month’s selection of readers’

wants and offers.

62 SCRIBE A LINE Letters and comment

from readers.

Regulars

PLUS

www.model-engineer.co.uk

CLASSIFIEDS EXTRA SUBSCRIBE ARCHIVE SUPPLIERS SHOP

HOME FEATURES WORKSHOP EVENTS FORUMS ALBUMS

7

WORKING

FOR THECLAMPDOWNBrian Moseley

describes the

construction

of a handy tilting

‘mini vice’.

This ingenious

design uses a

double clamp

beneath the

workbench forextra flexibility.



8/10/2019 mew225


8 www.model-engineer.co.uk Model Engineers’ Workshop

Let us look at the problems whenparting off. The blade digs in andbreaks or chatters or screeches like

a harpie which you will agree is very offputting, even when the top slide gibs aretightened right up and as much play aspossible is removed from the toolpost area.

Rear toolpost parting off is much better,it seems, than the normal front mountedmethod as it is usually more rigidlymounted, however the blade can still grabas the cutting forces applied tend to lift thesaddle assembly off the bed ‘V’ ways (assome well-known ‘gurus’ are wont to tellus). The same sort of reasoning wouldapply to the front or rear tool system

will be clear as mud. I also set up a DTI tomeasure any movement of the tool holder.

Disengaging the lathe drive train andswitching the machine off from the power, Ifound that by using only moderate handpressure to turn the lathe chuck in thedirection of rotation that the whole toolpostassembly leant towards the lathe centre by.019 inch, it could be forced further withoutmuch more effort. I stopped and made sureyet again that the entire toolpost assemblywas as tight as possible. It was so Iconcluded that any sort of resistance toturning would cause the blade to move intothe work taking an extra heavy cut andcausing even greater resistance to turning.

which would also tend to lift the tool awayfrom the bedways.

I decided to find out exactly whathappens using the normal arrangement onthe front toolpost. I drilled a small hole(4.9mm) in the end of a short piece of45mm round stock and as close to theedge as possible and bashed (technicalterm meaning force fitted) a short lengthof steel rod about 5mm diameter into thehole. This was chucked in the lathe. Theparting tool was set up as you would foruse and the tool wound in on the crossslide until the parting blade was just underthe protruding piece of rod and stoppingthe lathe from turning. Referring to fig. 1 it

Parting offin the metal latheWhat are the forces that make parting off such a chancy business? Rather thanjust theorising, Reg Merryweather actually did some experiments to fnd out.

1



8/10/2019 mew225


›

Partingblade

Toolpost

Top slide

Saddle

C/L

Blade holder

Plunger DTI

Mount

Small bolt about 20mmfrom lathe centre

Angle greaterthan 90º

C/L

DTI

DTILathechuck

Parting bladeholder & blade

ToolpostTop slide

Greaterthan 90º

Toolpost

Top slide

9

Parting Off Toolholder

February 2015

I now set up the DTI to read how muchthe tool holder moved sideways (fig. 2),Referring to the next drawing for the setup I used, I found that the tool holdermoved towards the headstock by .014inch, again this was using moderatepressure by hand to turn the lathe chuck inthe direction of rotation.

You will see from figs 1 and 3 that the

toolpost moves both toward the lathecentre line and also towards the headstockat the same time. What is happening toour parting blade that we ever so carefullyset up for the job that we were about topart from the bar? The poor blade is underpressure, so what happens? The tip of theblade is forced further into the work as theresistance to turning is felt, this causes theblade to cut deeper and this results ineven more resistance until somethinggives, usually the blade (and your temper)and results in your job being ruined andyour bar fridge taking a hit.

Now, if that is not enough problems, atthe same time the tool holder is movingtowards the headstock causing a sideloading on the parting blade resulting instress as shown above. These two forcesappear to strain the blade in such a way asto cause it to fracture in at least three bits(fig. 4).

Fig. 1

Fig. 2

Fig. 3

Rear toolpost parting

off is much better,

it seems, than the

normal front mounted

method as it is usually

more rigidly mounted.



8/10/2019 mew225


Blade holder

Stress

Stress

C/L

Toolpost

Top slide

Lessthan 90º


What are we going to do about it? Wehave to reduce the angle between thetoolpost centre line and the tool cuttingedge and the headstock centre to less thana right angle. This will cause the cutting

face of the tool to move away from thework when extra resistance to turning isfelt allowing, it is hoped, for the blade toclear its self.

Going back to our original set up, if wenow put our blade protrusion to theoperator side of the toolpost (fig. 5) andturn by hand once more in the direction ofrotation and read the DTI we find that thetool holder has moved the opposite wayto the previous reading as the angle is lessthan a right angle.

It is just too easy is it not? All we have todo is design and make a tool holder with apressure angle of less than a right angle.See photos 1, 2 and 3. This is the tool Imade cutting a washer of 45mm diameterat 280rpm and a feed rate of .00084 inchper rev. ■

Editor's Note: Reg has offered to preparea dimensioned drawing of his toolholderfor a future issue.

Fig. 4

Fig. 5

2 3

Parting off a washer with Reg’s holder. The construction of Reg’s toolholder is clear from this view.



8/10/2019 mew225

http://slidepdf.com/reader/full/mew225 11/67w w w . h o b b y m a g a z i n e s . o r g


8/10/2019 mew225



In operation there are two half nuts thatare engaged around the leadscrewwhen cutting commences, and are

disengaged at the end of the cut. Thecarriage is then wound back to the start,the depth of cut adjusted, and a newcut commenced. Screwcutting lathesnormally have a thread dial on the side ofthe carriage. This consists of a dial withnumbers on the periphery, connected to

a gear that meshes with the leadscrew.For a given thread pitch, charts indicateat which numbers the half nuts should beengaged. This only applies to a lathe withan imperial leadscrew cutting imperialthreads, or a lathe with a metric leadscrewcutting metric threads. When cuttingmetric threads on an imperial lathe, orimperial threads on a metric lathe, thehalf-nuts need to be kept engaged for thewhole screwcutting process.

One of the problems with screwcutting isfinishing the cut in the same place at eachpass. On an external thread the normalapproach is to have a runout, a sectionwhere the diameter is less than theminimum thread diameter so that once thetool runs into it doesn’t cut. This is relianton the operator opening the half nuts atthe correct time. Using runouts becomesfraught when cutting internal threads, as itis difficult to see what is going on. The

angle is 55 degrees, but for the US Unifiedseries, and metric, the angle is 60 degrees.What may be less well known is that thethread forms are not usually a sharp V

shape but have shaped roots and crests.The roots and crests are defined in thestandard for a particular thread form. For aWhitworth thread both the crest and rootare an arc with a radius equal to 0.137P,where P is the thread pitch. A full profileexternal Whitworth 8tpi insert is shown inphoto 2, showing the radius for root andcrest. The Unified thread ideally has flatcrests and roots, although in both casesrounding is allowed. An insert for cuttingan external Unified 8tpi thread is shown inphoto 3; the root is rounded, but the crestis approximately flat. The theoretical metricthread also has flat crests and roots,although the root is normally rounded forbetter fatigue resistance. An insert for anexternal ISO metric thread of 2mm pitch isshown in photo 4, showing a rounded rootbut a flat crest.

A full profile insert will cut one threadpitch only and correctly forms both the

consequences of not opening the half nutsat the correct time could be a crash,resulting in damaged tooling and work.

The introduction of carbide inserts for

turning tools allowed much higher speedsto be used, enhancing productivity. Manyinserts need to be run at high speeds toget the best finish. In due course carbideinserts became available for single pointthreading, and these too benefit fromrunning at higher speeds. Thisexacerbates the problem of disengagingthe half-nuts at the correct time.

Before looking at a solution to theproblem of high speed threading a fewwords about carbide threading insertsmight be useful. These normally come astriangular inserts, with three threadingedges per insert. Internal and externalthreading toolholders, with inserts areshown in photo 1. The inserts come inexternal and internal variants, and in twoforms, full and partial profile. Many readerswill be aware that different thread formshave different angles between the flanks ofthe thread. For Whitworth threads the

Fitting, Repairing and Using an

Ainjest High-speed

Threading UnitAndrew Johnston describes a useful device rarely seen inhobby workshops, but occasionally available second hand.

2 3

1

Insert Whitworth 8tpi. Insert Unified 8tpi.

Insert Threading Tooling.

A useful feature of a centre lathe

is the ability to screw cut threads

using a gear train between the

spindle and leadscrew to move the

carriage one pitch of the thread

per revolution of the spindle. The

pitch of the leadscrew and the

ratio of the gear train between

spindle and leadscrew determine

the pitch of the thread being cut.

The geometry of the thread is

determined solely by the shape ofthe cutting tool.



8/10/2019 mew225


›

13

Ainjest Automatic Threading Device

February 2015

crest and root. A partial profile insert willcut a range of pitches, but for an externalthread does not form the crest, and theshape of the root is a compromise. Apartial profile insert for ISO metric threadsis shown in photo 5. This insert will cutpitches from 0.5 to 3 millimetres. Note thatthe root radius is too small for the largerpitches, as it needs to be correct for athread of 0.5mm pitch. An insert for

cutting an internal thread is a mirrorimage of the external in terms ofclearances. What may not be quite soobvious is that the thread depth, and rootand crest shapes may be different, asspecified by the thread standard. Aninternal and external insert for ISO metric2mm pitch are shown in photo 6, internalinsert at the bottom. The different threaddepths and root radii can be clearly seen.

Ainjest High SpeedThreading UnitFor industrial lathes the problem of highspeed threading commensurate with thecapabilities of carbide inserts was solvedwith the addition of an Ainjest high speedthreading unit. The units were made bySaunderson & Costin, of Newbury, who nolonger appear to be in business. The unit isintended to sit on the side of the carriageand contains its own set of half-nuts thatengage with the leadscrew. Another featureis a lever underneath the unit that can beused to disengage the half-nuts via a tripmechanism. The disengagement is trippedby a settable block on a trip bar that runsthe length of the lathe bed. A variant ofthe basic Ainjest unit is required for eachtype of lathe to which it can be fitted, as thedetails of mounting and the positioning of

position ‘2’ is for fractional half tpi threads,eg, 4½ tpi, and position ‘4’ is for wholeinteger tpi. The screwcutting gearbox onthe lathe is set to cut the required threadpitch as normal. The half-nuts in the unitare then engaged with the leadscrew atthe correct point, as allowed by slots in adisc on the silver knob, and using theblack operating handle in a similar way toengaging the half-nuts during normal

screwcutting. At the end of the pass theunit trips and disengages the half-nuts.The thread is cut using as many passes asare required as for normal screwcutting.

Damage and a Repair SchemeWhen first using the unit I made afundamental error, and damaged themain casting on the Ainjest unit. Havingcut a trial thread I decided to clean up thediameter of the workpiece before cuttinganother thread. A simple procedure, swingthe toolholder to a normal turning tool anduse the power feed to move the carriage.My mistake was that I had not movedthe trip lever to the safe position. As thecarriage moved under power feed the triplever engaged the trip block but since thethreading unit was not engaged the tripmechanism didn’t trip, but just presentedan increasing load on the bracket holdingthe trip lever. The lathe started to sound abit laboured and I knocked the power off,but not early enough. The trip lever sitson a cantilever bracket with two screwsinto the unit main casting. This had beensubject to a large twisting force whichbroke the casting around one of the screwholes, see photo 8. I took the unit off thelathe, and it sat on the bench for abouta year while I considered possible repair

the leadscrew will be different. My latheis a Harrison M300, and is imperial. Adifferent, and rather more complex, Ainjestunit is required for metric lathes. A pictureof the Ainjest unit fitted to my lathe isshown in photo 7, with the trip bar labelled.

Fitting and Usingthe Ainjest UnitGiven that the Ainjest unit I obtained wasintended for my lathe, fitting it was simplya case of fitting bolts into the carriage asrequired. Tapped holes in the carriagewere already present, presumably frommanufacture. The unit replaces the normalthread dial indicator, which becomesredundant. On my lathe the lever withthe red knob (spindle power - down forforward, up for reverse) that normallysits on the right hand side of the carriagesimply moves to the right hand side of theAinjest unit. The trip bar that came with theunit was intended for a 25 inch betweencentres version, whereas my lathe is 40inches between centres. I simply replacedit with a longer length of standard ¾ by ¼inch cold drawn bar. Machined pads andtapped holes for fixing the trip bar werealready present on the lathe.

Using the unit is simple. The settableblock on the trip bar is moved to theappropriate place and locked with a setscrew. The trip lever underneath the unit ismoved from its safe position so that it cancatch the block when the carriage is at thecorrect place. The round silver knob at thetop of the unit is moved from position ‘0’,which is the safe position and will notallow engagement of the half-nuts, to oneof three operating positions. Position ‘1’ isfor fractional quarter threads, eg, 3¼ tpi,

4 6

8

5

7

Insert ISO Metric 2mm. Inserts Internal and External ISO Metric.

Damage to Main Casting.

Insert ISO Partial Profile.

Ainjest Unit Fitted.



8/10/2019 mew225



schemes. The unit mirrors changes inindustry during the second half of the20th century, in that the vertical holesare threaded M5 but the horizontal holeis threaded 5 ⁄ 16 BSW. Eventually I decidedthat the best plan was to completelyreplace the area of the casting thatcontained the M5 and 5 ⁄ 16 BSW threads.Measurement of the unit and modelling inCAD, using imperial units, showed that Icould fit a block and have room for fixingbolts. The partially disassembled unit, andthe new block (bottom left) are shown inphoto 9. The block (machined from gaugeplate) is fitted to the main casting withtwo vertical M4 bolts and two M4 bolts infrom each side. In photo 9 it can be seenthat the casting has the central portionmilled away ready for the new block. Ididn’t completely dismantle the unit whenmachining the casting, but paper wastaped all around the mechanism, and tothe mill table to prevent ingress of the castiron swarf and dust. Photograph 10 showsthe repaired and re-assembled unit. Itwould have been better if I hadn’t brokenthe darn thing in the first place, but at leastthe repair is reasonably neat.

Examples of Using the UnitIn photo 11 are some parts which havescrew threads cut using the Ainjest unit.The fine threads are 50mm diameter, 26tpiWhitworth form threads. The diameteris metric because I design in metric, butthe threads are Whitworth because mylathe is imperial. These parts form aone-off experimental jig, so the actualthread doesn’t matter. However, a closefit is required, as when screwed togetherthe enclosed chamber is subject to waterpressure at 250psi. The internal thread isshown in close-up in photo 12. The threadis within one pitch of the bottom of thepart. To set the trip for the internal threadproceed as follows. The trip block is roughlyset and the half-nuts engaged, the unitmoves and then trips, with the tool wellclear of the work. Once it is ascertained that

have found that above about 800rpm, forfine pitch threads, it is difficult to getconsistent engagement of the half-nuts.For coarser pitch threads a slower speed isadvisable. On the parts shown in photo 11the coarse thread on the left, ¾ BSP, wascut using the Ainjest unit at 500rpm.

Cutting Metric ThreadsMy lathe is imperial, and while it hasmetric pitches incorporated into thegearbox the half-nuts need to be keptengaged when cutting a metric thread.Clearly this is not possible when using theAinjest unit, as it automatically disengagesthe half-nuts at the end of a cut. There isa piece of equipment, called a Metradial,that can be used in conjunction withan imperial Ainjest unit to cut metricthreads. Essentially this is a thread dialindicator. There is a company in the UK

the tool will not crash into the work, theunit can be engaged and tripped again, butthis time with the tool inside the work. Thedistance from tool to work can then be finetuned by using the compound slide. I used aclearance of 10 thou.

Another example of a screwcut threadusing the Ainjest unit is shown in photo13. This is an embryo hob, made fromsilver steel, for free hobbing a 4 inchdiameter 22 tooth worm wheel. I find that Iget a better finish on silver steel at higherspeeds, hence the use of the Ainjest unit.The thread is another odd one; the shankdiameter is 25mm, but the thread is 20tpiWhitworth, so that it will fit a Clarksonmilling chuck collet.

The Ainjest manual states that threadscan be cut at up to 3000rpm. However, atthese speeds considerable loads would beexerted on the half-nuts, and the unit, asthey accelerate the carriage. In practise I

10

11

Unit Reassembled.

Parts with Screwcut Threads.

9

New Part Ready for Assembly.



8/10/2019 mew225


15

Ainjest Automatic Threading Device

February 2015

an integer multiple of 6.35. However, thesenumbers, like 57.15, are not convenient.Another possibility is to return the spindle,

leadscrew and carriage to the sameposition at the start of the thread for eachpass. The spindle and leadscrew aregeared together, so returning the spindleto its starting point will suffice. Resettingthe position of the carriage is simple usinga bedstop. Resetting the spindle is moreinvolved. My solution involves fitting arotary encoder to the spindle and countingthe number of revolutions while doing acut. If the lathe is then reversed and thecount taken back to zero, the spindle, andleadscrew, should be in the originalalignment. In practice it would be prudentto use an encoder disk with many lines,say 360, per revolution. It would also besensible to go beyond ‘0’ before comingback, in the same way as when accountingfor backlash. The setup will get built whenI have a pressing need to cut metricthreads using the Ainjest unit. ■

Suppose we are cutting a 0.45mm pitchthread. From the start if we turn the spindleby whole turns then the spindle and

leadscrew will be in the same orientationwith respect to each other when:

6.35m = 0.45n

where both m and n are integers.Multiplying by 100 we get:635m = 45n

And dividing by 5 gives:127m = 9n

Now 127 is a prime number so theequality cannot be further factorised. Som=9 and n=127. Going back to the pitchesinvolved we have:6.35x9 = 57.15 and 0.45x127 = 57.15

Extending to other metric pitches we seeby examination that the metric pitchmultiplied by 127 gives a number that is

that purports to sell the Metradial, but theydo not seem to be active. The Metradialis intended for use on imperial lathes

that have an exact conversion to metric,i.e. there is a 127 tooth gear in the geartrain from spindle to leadscrew. If themetric conversion is not exact then theMetradial will still function but there willbe a cumulative angular error at eachsuccessive pass. This can be amelioratedby either cutting the thread in a minimumnumber of passes, or advancing thecompound slide by 0.0035 times thethread pitch (in millimetres) at each pass.My lathe falls into the latter category, asit incorporates the ratio 288/7315 in thescrewcutting gearbox.

In essence the problem of cutting metricthreads on an imperial lathe is one ofgetting the spindle and leadscrew back intothe alignment they were originally in, forsubsequent cuts. This is essentially aproblem in integer arithmetic. My leadscrewis 4tpi, so the pitch is ¼ inch, or 6.35mm.

12 13

Detail of Internal Thread. Embryo Hob with Screwcut Thread.

Pick up your copy today!

Coming up in Issue 4500

Content may be subject to change.

• The Southwold

Shunter: A short

construction

series using Tich

castings.

•

MEX Report:The Competition

• Make a Six

Tool Turret

• Out and About

Part 2

• FOCAS

Crankshaft



8/10/2019 mew225


3 ISSUES FOR £1Then £16.00 every 6 months




WWW.MODELCOLLECTOR.COMC O L L E C T O R

OUCH!Howtoavoid/fixexpensivedamage

TROJANALERTArareDinky promotionaltobeonthelookoutfor

A.R.CLASSICSThemissinglinkintheadoptionof1:43scale?

READER SHOWCASESteveDilworthinvitesusto joinhimonaGreenGoddessodyssey

Wereportbackfromthepresslaunchfo rBritains’ fabnewJCB models

Wereporpresslau

GREAT EXCAVATIONS!

CHRISTMASCOMES EARLY!12 fabulous highvalue prizes tobe won andthe choiceis yours!

LATEST MODELS ReviewedandratedHonest,unbiasedopinion

nRH

UK’SNO.1

GUIDE

NE WRELEASES

C O L L E C T I N G G R O U P XMAS2014

£3.75

C e XM S 2 b i 1Coverlines XMAS 2014b.indd 1 1 1 2 1 311/11/2014 14:34


N o . 2 2 3

DECEMBER2014


£ 4 .2 0

ENGINEERINGGROUP

MODEL ENGINEER EXHIBITION2014 SHOW GUIDE INSIDE!

Jointheconversationaboutthisissue:www.model-engineer.co.uk

C O VER FE A TUR E

PrecisionMilling VicePlans & Details ofMike Checkley’sCompact Design

FOCUS ON MILLINGHigh Speed Spindle Adaptor

Aligning a Benchtop Mill

Self-Release Drawbar

Milling on an ML7

190 7- 2014

www.mode le ngineersh

12-14D ecember 2

014Sandow nPa

rkRa cecourse

O PEN INGHOURSF

r id a y , 12 th a nd S atu r d ay ,13 th10 .0 0

am- 5 .0 0 pm(L a sta d miss ion :4 .0 0 pm)

Su n da y ,1 4th10 .0

0a m- 4 .0 0p m(L as ta dmis sio n :3 .0 0p m

)

Com

petiti onCl asses FreeSMEELect

ures WorkshopDemonstrati ons

TradeStands

Cl ubs&Societies

Meet theM

akers!

SHOW GUIDEFREE

FREE VINTAGE WORKSHOP PRINT

MEW 223 Cover.indd 1 05/11/2014 10:42





DECEMBER 2014

TM

MAG AZ INE

THE WORLD’S BEST PHILATELIC MAGAZINE

NovaScotia’seye-catching1860designs

FulldetailsofRoyalMail’sChristmasissueinallits manyguises

Cataclysm of the Great War

HailtothealeStampsandcovers onthethemeof beer

Chalk-surfacingWhythesilver testdoesn’talwayswork

How the postal service wasrevolutionised, brutalisedand tested to breaking pointin 1914-18, but emergedstronger than ever

WerepostagestampsinventedinSlovenia?

w w w . s t a m p m a g a z i n e . c o . u k

£ 3 . 9 5

C O L L E C T I N G G

R O U P

VER mustard.indd 1 24/10/2014 11:44




TERMS & CONDITIONS: Offer ends15th March 2015. *UK offer only. DD only. Prices above indicate thePrint Only Subscriptions follow on prices. Print + Digital and Digital Only Subscriptions are also availablethrough this offer; prices are available online or can be advised via our customer services line by quotingthe code above. For full terms & conditions visitwww.mytimemedia.co.uk/terms . From time to time,your chosen magazine & MyTimeMedia Ltd may contact you regarding your subscription, or with detailsof its products and services. Your details will be processed in full accordance with all relevant UK and EUdata protection legislation. If you DO NOT wish to be contacted by MyTimeMedia Ltd & your magazineplease tick here:

Email

Post

Phone. If you DO NOT wish to be contacted by carefully chosen3rd parties, please tick here:

Post

Phone. If you DO wish to be contacted by carefully chosen 3rdparties, please tick here:

Email.

I I * l l i i i

SEND TO: MYTIMEMEDIA SUBSCRIPTIONS, Tower House,Sovereign Park, Market Harborough, Leics LE16 9EF

Try any title for £1*

Have you made a New Year’s Resolution yet? This year, why not make it to spend time

on a hobby you’ll really enjoy? To help you out with this you can try any of our magazines

below for just £1 with no obligation to continue! You could even treat someone else…

• GREAT RANGE OF HOBBY TITLES TO CHOOSE FROM

• NO OBLIGATION TO CONTINUE

• GREAT FUTURE SAVINGS

• DELIVERED CONVENIENTLY TO YOUR DOOR

OtherSubscription

Packagesavailableonline!

SUBSCRIBE SECURELY ONLINE: www.mymagazineoffers.co.uk/NY15CALL 0844 543 8200 and Quote NY15

BY POST: Please complete the form and return it to the address provided below. Quote Ref: NY15

Name:

Address:

Postcode: Email:

Tel: Mobile:

Banks and Building Societies may not accept Direct Debit

instructions for some types of accountReference number (to be completed by My Time Media)

Branch sort code Signature

Account Number Date

Account in the name(s) of:

Instructions to your bank or building

society: Please pay MyTimeMedia Ltd.

Direct Debits from the accountdetailed in this instruction subject to

the safeguards assured by the Direct

Debit Guarantee. I understand thatthis instruction may remain with

MyTimeMedia Ltd and if so, details will be passed electronically to my

Bank/Building society.

2 5 6 2Originators Identification Number 4 2

To the Manager: Bank Name

Address

Postcode:OFFER CODE NY15

Please start my subscription to Magazine name

for £1, and then every monthsPrice

N e w Y e a r

S p e c i a l

✁



8/10/2019 mew225


›

17

Science of Steel

February 2015

Hardening carbon steelsRoughly speaking, the hardening processtoday is only a refinement of what Ilearned back at the forge: heat thenquench. The back story is a little morecomplicated. First, the metal must be inthe all-austenite state, meaning abovethe UCT. Second, you need to know thatquenching forms an entirely new phasecalled martensite. Yes, another ‘ite’word. There are at least eight in the steelliterature; this article talks about only five.Martensite is responsible for tool steel'suseful qualities.

Consider the case of an ordinary toolsteel like O1 or W1. Looking at the Fe-Cphase diagram, which depicts equilibriumconditions, we know that the metal mustbe entirely austenitic above the UCT, withall of its carbon (say 1%) dissolved into thewide-open spaces of FCC iron. Slowcooling through the UCT and belowchanges the composition to a mix ofaustenite and cementite. With further slowcooling below the LCT this is transformedagain into cementite and pearlite. Theseprocesses take time.

But what if you don't allow the time?Suppose you quench it, cool it veryrapidly, such as 2000˚F (1100˚C) persecond. Unsurprisingly, this causes aviolent, near-instantaneous transformationfrom austenite to something else entirely,

namely martensite. Theoretically,martensite is all there should be injust-quenched steel at room temperature;in practice the martensite content may beas low as 60% or so, the remainder beingaustenite that didn't make the cut.

The change to martensite is dramaticindeed, like the shattering of safety glass.In a fraction of a second we have gonefrom the 14-atom FCC austenite to astretched version of the 9-atom BCC, yetwithout losing any carbon, thuspreventing the formation of pearlite. Thenew ‘martensitic structure’ is called a BodyCentered Tetragonal, BCT (fig. 6).

Martensite is indeed a phase, but it ishighly unstable and therefore doesn'tappear on the phase diagram. It is a veryhard and brittle form of steel with ahardness close to 65 RC (Rockwell ‘C’scale), about the same as high speedsteel. Martensite comes with a lot of

Heat Treating

O1 & W1 Tool SteelsRichard Rex has discoveredthat understanding thescience behind steelleads to better resultsin the workshop.

Until a year or so ago all I knew about hardening carbon steels was summed

up in the one-liner: ‘Heat to cherry-red, then quench in water’. You then

tempered the piece – reduced its brittleness – by heating it to a lower

temperature and re-quenching. I learned that as a blacksmith's assistant

(more accurately, gofer), and have applied it ever since making scrapers,

chisels and – now and again – milling cutters such as D-bits and counterbores

from O1 and W1 tool steels. Now and again says it all: I didn't make them

regularly enough to be troubled by quality control. Some cutters would last

forever, others died in a minute or two, oh well. That's how it stood until a

couple of recent failures prompted a closer look. This article is the result.

It focuses on the O1 and W1 alloys because they are inexpensive, easily

machinable in the model shop, and available overnight in a huge range of flat

and round sections (especially O1).

Part 2

Fig. 6The structure of martensite

This is how iron atoms are arranged in martensite. It is a stretchedcube called a Body Centered Tetragonal, BCT. Like BCC it has asingle atom at its center but its properties are quite different.



8/10/2019 mew225



internal stress and strain which, asyou've guessed, we can relieve to thedesired degree by cooking at a lowtemperature – in other words, bytempering.

What does temperingactually do?This is a question that gets evasiveanswers, if any, mainly because themetallurgy is very complex. At the practicallevel we know that tempering makesthe workpiece a usable tool, tradingits hardness/brittleness for toughness.Tempering is a slow process, taking anhour or more in the oven. The short versionof the story is as follows. Temperingstabilizes the steel in three stages:

1) By forming in the martensite very small‘intermediate’ carbides (relatives ofcementite, but not quite the same),then;

2) By decomposing retained austenite intoferrite and intermediate carbides, and;

3) Finally, by replacing the intermediatecarbides with their more stablecounterpart, cementite, Fe

3C.

Now, back to the shopDo you really need to know all thataustenite, cementite, martensite stuff forpractical heat treatment? No, but it helpsto talk the talk when your project calls foradditional background.

The rest of this article describes the heattreatment of two machinable steels, O1and W1, in the reverse order – W1 first,because it's more convenient, less messy,and it doesn't create odors and smoke (‘W’means water-hardening, ‘O’ oil-hardening). What's special about O1 andW1 is that they are inexpensive, readilyavailable, and machinable with regularHSS cutters – go slow, shallow cuts. Think15 thousandths, 10 or even 5 until youhave the feel of it. (The photo at the end ofthis article shows a shop-madecounterbore being machined from W1 in aspecial fixture that is used for both initialmilling and edge grinding.)

How do you knowone W1 from another?If you started at the top, you already knowthat W1, a.k.a. drill rod (‘silver steel’ in the

UK), comes in various grades, meaningdifferent percentages of carbon fromcontent. Suppliers will usually tell youonly that their W1 is W1, end of story.Lacking definite specs, we have to assumethat W1 is 1% carbon. (A close relative ofW1 is 1095, with 0.95% carbon). For 1%carbon steel we know from the Fe-C phasediagram that its UCT will be approximately1500˚F (815˚C), the pre-quenchtemperature. This is only a few degreeshotter than the magnetic transition point,1418˚F (770˚C), and so can be predictedreliably with a magnet.

W1 chemistryW1 is a water hardenable steel, inproduction for well over 100 years. Its‘case hardness’ and malleable core makesit, even today, the steel of choice for thebest kitchen knives. W1 is a very basic

1

A mini-kiln for heat treating.

alloy, usually with only two componentsother than carbon (in silver steel there isalso around 0.35% chromium):

the gas when the quenching temperatureis reached. None of this applies, ofcourse, to the lucky few with furnacesand precision pyrometers: no need formagnets in that kind of setup – just let theworkpiece cook for the necessary time atthe desired temperature, then quench itimmediately.

A propane torch flame is approximately3,600˚F (1,980˚C). In theory that could meltsteel, but it won't. Even with a heat shieldof firebrick, you'll be lucky to get apea-size piece of it hotter than 2,000˚F(1,100˚C - orange to yellow). Oxy-acetyleneburns at over 6,000˚F (3,300˚C), givingplenty of headroom for anything youmight want to do, including welding (but itcan also overheat a small workpiece in amatter of seconds). In between the two isMAP-Pro (3,700˚F, 2,070˚C). MAP-Pro ispropylene, not to be confused with thehotter-burning MAPP gas, which has notbeen produced in the USA since 2008.

If yours is a non-igniting ‘two-hand’ torchyou might want to have an assistant onhand for the minute or two it takes to bring

a workpiece up to quenching temperature.

The heat treatment setupThe best place for heat treatment is outsidethe shop; fumes are less of an issue and,provided you have eye/face protection,water splashes from quenching are low-hazard. Most of us work inside, with afume hood if we're fortunate, reasonableventilation if not. If you are relying on‘heat colour’ to judge temperature, thebest conditions are a gloomy day or lateafternoon, no direct sunlight.

A welding table with steel top makes anideal workbench for heat treatment, butthere is no need for anything special.Provided its surface is protected from heatwith (say) an inverted oven tray, a woodentop bench will do equally well. I use a minikiln constructed of firebricks to focus heaton the workpiece, the only way I know toheat evenly with a torch. Even heating is amust in heat treating.

Table 2: Composition of W1 Steel

Typical chemistry of W1

Carbon 1%

Manganese 0.25%Silicon 0.2%

If your W1 really does have a highercarbon content, say 1.2%, its UCT of1650˚F (900˚C) will be way beyond themagnetic transition. All you can do in sucha case is rely on the hot colour – ‘brightcherry red’ – or, better, use a temperature-sensitive crayon such as a Tempilstik.Super-accurate control of the pre-quenchtemperature is not often necessary in themodel shop, but serious over-heating maycause permanent damage to the surfacesyou've carefully machined (so buy aTemplestik for pre-quench temperature if

you plan to do a lot of heat treating).

Size of workpieceto be heat treatedThe counterbores and other cutters I amthinking of would range from 1/8 to ¾ inchdiameter. There is nothing to stop youworking with larger diameters, but bearin mind that you will need greater heatingcapacity – possibly beyond a regularpropane torch.

A word on torchesIdeally you'll want to use a ‘one-hand’torch, the piezo-electric sort that self-igniteand self-extinguish – press and hold aspring-loaded button to light, release toextinguish. You cannot be holding theworkpiece at the same time as you turnon the gas, then light the torch with aflint striker. Even worse and potentiallydangerous, you don't have time to turn off



8/10/2019 mew225


›

19

Science of Steel

February 2015

2

Use an old toaster oven for tempering.

The few minutes it takes to build a kilnwill be repaid many times over. Highlyrecommended! There is nothing criticalabout the dimensions; insidemeasurements of the kiln in photo 1 are 1x 1½ x 2½ inches. The lid is loose fitting,with a small gap at the rear to controlblowback. It is made of soft firebrick froma kiln supplies company such as Bailey(their catalog reference: K23). One 9 x 4½ x2½ inch brick is all you'll need; simply cutit into ¾ inch thick sheets using any typeof handsaw, but not one you care about.Stabilize the construction using sawn-offnails as dowel pins in 1 ⁄ 8 inch holes (use anold drill in a hand chuck, no need forpower). The downside of this is cost; thebricks themselves are inexpensive, butshipping is not. Two alternatives: buy onefrom a local potter who does his/her ownkiln work, or build a different design usingthe smallest conventional firebricks youcan buy from a masonry supplier.

For small W1 tools you need only quart(litre) or two of water (or brine, see inset)in a disposable metal container such as a

coffee can. This needs to be positioned soyou can plunge the workpiece quicklydown into it with the minimum of aircooling on the way. For most purposeswater quenching works fine for W1, butmany prefer brine because it creates aprotective coating around the steel as it isquenched, enhancing hardness byreducing decarburization scale. Use a 10%solution of ordinary table salt in water(start with a piece of raw potato in plainwater, then add salt until the potato risesto the surface). Another way to arrive atthe same point is to add about 3 ounces ofsalt to each quart of water.

If you plan on using the ‘magnetictransition’ to judge the pre-quenchtemperature, you will need to clamp yourmagnet to a rigid stand so you can tap itfrequently with the workpiece whenheating. Practically any magnet will do thejob (suggestion: ½ inch diameter rareearth magnets from Lee Valley sell forabout $1 apiece).

Wear wraparound safety glasses toprotect against hot water splashes.

TemperingThe blacksmith I trained with wouldtemper a quench-hardened tool bybrightening its surface with a file, thenreheating its shank until the oxidation

colours travelled toward the businessend. When the leading colour (‘lightstraw’, 450˚F, 230˚C) reached the tooltip, he re-quenched immediately to ‘fix’the temper. This is not recommended for small precision cutters – we are notmaking pry bars here. The main problemwith tempering small tools this way is thatonce the colours appear at the shank endthey get to the tip so fast you are almostbound to overshoot – which means toosoft an edge. Aside from unpredictablehardness, re-quenching can leave the toolin a fragile, stressed condition.

We will use an oven instead, noquenching. In contrast to the hit-or-missmethod it takes no effort, and is 100%predictable. The tempering oven can be asbasic as a second-hand toaster oven, but itdoes need fairly accurate temperaturecontrol. Photograph 2 shows one demotedfrom kitchen use some years ago, but it

works well for heat treating. Note thesecond wire rack to prevent small partsfalling through, and the thermometer – alot more reliable than the oven's hit ormiss temperature control.

It also needs a tray to keep workpiecesoff the oven floor, ideally something like acooling rack for baked goods – not a flatsheet of metal. Decide on the desiredhardness of the finished tool, then choosea temperature from Table 3.

Instead of relying on the dial markings,use at least one oven thermometer (two,better), and allow 20 minutes or so for thetemperature to stabilize. Allow theworkpiece to remain in the oven for atleast 1 hour (more, say 2 hours, for ¾ inchdiameter and up), then turn off the ovenand allow it to cool to room temperature.Within reason you can speed up thecooling process by removing theworkpiece from the oven after thetempering session and allowing it toair-cool on a kitchen-style rack (not aninsulating material such as firebrick).Avoid thermal shock. There is no harm atall in leaving the workpiece in the oven for

more than the specified time; you cannotover-temper it (but that doesn't apply tothe pre-quench ‘soak’ time, which needs tobe close to the book).

W1 heat treating procedureFirst, make sure that the tempering oven isat the desired temperature (see Tempering above), because you will be transferringthe workpiece to it immediately afterheating and quenching – which takes onlya few minutes.

Bearing in mind the need for evenheating, the following assumes you areusing a mini kiln to concentrate the torchflame. With the workpiece held in an oldpair of pliers or (better) a custom clamp,place it in the kiln leaving a short length ofits shank protruding. Starting at the shankend, heat it with the torch while watchingfor colour changes. Bearing in mind that a

½ inch rod will take a good minute or twoto come up to temperature, don't confusethe red hot glow of the firebrick (almostimmediate) with the temperature of theworkpiece. If you have a magnet on hand,use it to calibrate your sense of colour-temperature; while the workpiece isheating, remove it periodically from thekiln, then tap it against the magnet. Whenmagnetic attraction ceases (dark-to-cherryred region) the workpiece is almost atquench temperature. Noting the colour,aim for a shade hotter, then – important –hold that temperature for a soak timedepending on workpiece diameter: from 1

minute (1 ⁄ 4 inch) to 2 minutes (1 ⁄ 2 inch) to 5minutes (1 inch).

Because lighting conditions vary, andtherefore one's perception of colour, youmight want to calibrate using the magnetevery time you heat treat. Don't overheat! As steel is heated beyond 1000˚F (540˚C- visible heat) its surface begins to shedcarbon, and scaling (flaking) appears. Thisis ‘decarburization’, to be avoided to theextent possible (a decarburized surfacehas practically no hardness). Even with apropane torch you can damage any sizeworkpiece by decarburization. If this turnsout to be a real problem in yourapplication, use an anti-scaling powdersuch Rose Mill PBC. Start the heattreatment process in the usual way, thenstop when the workpiece is at 500˚F(260˚C). Dip the workpiece into the powder(which will melt), then continue to heatand quench.

Table 3

OvenTemperature

Rockwell ˚C

Scale Hardness

300˚F 150˚C 64

400˚F 205˚C 61

500˚F 260˚C 59

600˚F 315˚C 55



8/10/2019 mew225



Table 4 – Typical hardness of various tools

Product Rockwell˚C ScaleHardness

Micro-grain carbide 79

High Speed Steel 65

Files 65

Case hardened dowel pins 59

Single edge razor blades 58

Wood chisels, plane blades 58

Hobby knife blades 56

Locking pliers 55

Hex wrenches, screwdrivers 50

Machinistʼs scales (rules) 49

Axes 45

Socket head cap screws 42

Wood scrapers 38

Table 5

Typical chemistry of O1

Carbon 0.9%

Manganese 1.1%

Chromium 0.5%

Tungsten 0.5%

Table 6

OvenTemperature

Rockwell ˚C ScaleHardness

300˚F 150˚C 63

400˚F 205˚C 60

500˚F 260˚C 57

600˚F 315˚C 54

After the specified soak time, be sure theworkpiece is evenly heated all the wayround – take a very quick glance – thenplunge it vertically into the water or brinewith a rapid up and down motion toprevent the formation of air pockets thatslow the quenching. Wipe off theworkpiece, then transfer it without delay to the already-heated tempering oven.Here I'm quoting Dave Smucker(Tidewater Blacksmiths), who says that– like me – he used not to pay muchattention to the ‘without delay’ part, but itis important. He points out that aquenched part is in a highly stressed state,and wants to relieve that stress bycracking. Speedy transfer to the temperingoven will avoid that issue, but, before youtemper the steel check its surfacehardness with a file: if you have done theheating and quenching right, the file willskate freely over the surface – dead hard.If the file bites at all, the steel is too softfor use as a tool. Be sure to check for evenhardness all around the tool. Don't wasteoven time on a soft tool.

If the tool is not evenly hardened youcould try heat-treating it again, but first itneeds to be annealed . The problem here,at least in theory, is that annealing takesan hour or more at ‘orange red’ (about1600˚F, 880˚C), well above the UCT,followed by slow cooling. If you don'thave a furnace, the best you can do is holdthe annealing temperature for a fewminutes, then allow air-cooling to roomtemperature. This won't be a perfectrestoration of pre-quench chemistry, but itmay be enough to get by without re-making the tool. Table 3 shows temperingtemperature vs. average hardness values(R

C) of W1. W1 hardness as quenched is

approximately RC

67. These numbers arefrom Heat Treatment, Selection andApplication of Tool Steels by William E.Bryson.

How hard should my cutter be?Most of the cutters we use every day arehigh speed steel, HSS, typically M2 alloywith a hardness of R

C65. The theoretical

hardness of W1, as quenched, is RC 67, but

you cannot use it in that condition. Withouttempering, it is dangerously brittle.

You may wish to do your ownexperiments on hardness (= cuttingability) vs. brittleness. Assuming you aremaking cutters such as countersinks or

counterbores, start by tempering at 350˚F,the usual choice for W1 (for an evenharder tool, you could go as low as300˚F). Finish the tool by grinding orhand-honing with a diamond lap, thentest it on the mill or drill using coolant toavoid ‘drawing its temper’ (softening) byover-heating, see Grinding and usingcarbon steel cutters , below. If cracking isan issue, reduce the hardness for the nexttry by raising the oven temperature a fewdegrees. In general, use the lowesttempering temperature that makes sensefor your application. See table 4, thoughthese numbers are fairly arbitrary,depending on manufacturers' preferences(and quality, which is all over the map –literally). The idea for this table camefrom Machine Shop Trade Secrets byJames Harvey, an excellent reference forall machinists, not just those ‘in thetrade’.

Why O1 instead of W1?You will find O1 (in Europe, typically gaugeplate) somewhat harder to machine thanW1, its quenching medium isn't free, andits hardness as-quenched is a tad lower.So why use it at all? The answer is thatO1 offers a good all-round compromise ofmaterial cost, machinability, toughness,wear resistance, and a wider range ofavailable shapes and sizes,. It dependswhat you want your cutters to do. If youare cutting just a few dozen holes in mildsteel, W1 will do the job. For a longer-lasting tool, go with O1. Just bear in mindthat careful heat treatment can be moreimportant than your choice of one versusthe other.

O1 chemistryO1 is a ‘higher’ alloy than W1, meaningit has more components. Most suppliersagree that its carbon content is 0.9%. Itcontains four times more manganesethan W1. This is a carbide-formingelement which, like the other additionalcomponents, chromium and tungsten(and sometimes vanadium up to 0.3%),enhances toughness in the tempered steel.

oil viscosity, oil chemistry and agitation of the workpiece in the quench bath. Thehigher the H value, the harder the steel.In ballpark terms, water quenching is 5 to8 times more severe than oil quenching(brine even more so – about 10 times).

Commercial quench oils have proprietaryadditives to achieve fast, uniform quenchingwith the minimum of side effects. Most areavailable only in bulk, 5 gallons or more.The smallest quantity you can buy of anydedicated quench oil is probably 1 gallon,from McMaster Carr, more than you'll needin decades of heat treatment. At the time ofwriting this was available in two ‘speeds’, 11and 28 seconds, which define theirperformance as measured by the GMQuenchometer, an industry standard. Formodel shop applications the 11-second typeis recommended. Good results can also beobtained using a generic mineral oil such asbaby oil. Vegetable oils are too viscous(poor heat removal), and are notrecommended.

O1 heat treating procedureAside from the quenching medium, thereis very little difference between the O1and W1 processes. Use the same numbersas W1 for pre-quench temperature andsoak times, ditto for tempering. Whenquenching, be sure to move the workpiecevigorously up and down to promoteeven cooling. Have caution, unlike waterquenching, oil quenching leaves the steeldangerously hot , even if you leave it inthe oil bath a minute or more. Table 6shows Tempering temperature vs. averagehardness values (R

C) of O1. O1 hardness

as quenched is approximately RC 66.

These numbers are from Heat Treatment,Selection and Application of Tool Steels byWilliam E. Bryson

Quenching oilIf you were to believe the web gossipyou would think O1 can be quenchedwith just about anything, from usedmotor oil to Canola. That might be OKfor some applications, but in the modelshop we need more control. The keyfactor is ‘quench severity’, a measure ofhow fast heat is removed from the steel.This is the H parameter: it depends on

Grinding and using

O1 and W1 toolsThe bottom line on the subject is this: ifthe cutting edge of an O1/W1 tool exhibitsany discoloration in use or when beingground, its performance is compromised– terminally. It's that simple. Even a lightstraw colour indicates 450˚F (230˚C), wayhigher than tempering temperature, so thetool is now softened. In some cases it maybe worth annealing and heat treating allover again, but it may better to machine areplacement tool from scratch.

Avoiding this problem in use is simply amatter of taking shallow cuts, at the sametime keeping the tool cool with anappropriate supply of, yes, coolant.

Grinding is something else again. Witheven the lightest pressure on the wheel atool can be scorched in a matter ofmilliseconds. This is why, back in the daywhen HSS (high speed steel) was a rarity,grinders were supplied with a water



8/10/2019 mew225


21

Science of Steel

N o . 2 2 3

D E C E M B E R 2 0 1 4

T H E E S S E N T I AL MAG AZ I N E F O R E V E R Y H O B B Y E N G I N E E R

£ 4 . 2 0

EN GI NE ER IN G GR O UP

MO D E L E N G I N E E R E X H I BI T I O N 2 0 14 S H O W G U I D E I N S I D E !

J o i n t he c o nv e r s a t i o n a b o u t t hi s i s s u e : w w w .m o d e l - e n g i n e e r .c o .u k

CO V ER FE AT UR E

P r e c i s i o n Mi l l i ng V i c e P l ans & D e t ai l s o f Mi k e C he c k l e y ’ s C o mp ac t D e s i g n

F O C U S O N MI L L I N G H i g h S p e e d S p i nd l e Ad ap t o r Al i g ni ng a B e nc ht o p Mi l l S e l f -R e l e as e D r aw b ar Mi l l i ng o n an ML 7

1907 - 2014

w ww .m od e l en gi nee r sho w .co .u k

12 - 14 D ec e mb e r 2 0 14 S an d ow n Pa rk R ac ec o ur se

O P

EN I N GH O U

R S Fri da

y,12th andSa

tur day ,1 3th1 0. 00

am-5 .00pm(

Lasta dm i s si on:

4.00p m ) Sun d

ay , 14 t h

10 .00am -

4. 00 p m( Las t

admi ss i on: 3.00

pm)

■ Com p

eti t i o nCl a ss

es ■ Fr ee S

M EE Lectu r e

s ■ W or ks ho

p D em ons tr

at i on s ■ T ra deS ta

nds ■ Cl u b

s &S o ci et i es

■ M ee t

the M a kers !

S H OW G U I D E

F R E E

F RE E V I N T AG E W O RK S H O P P RI N T

M E 2 2 3 C ov er .i nd d 1

0 5/ 11/2 0 14 10 :42

Please reserve/deliver my copy of Model Engineers’ Workshop

on a regular basis, starting with issue

Title First name

Surname

Address

Postcode

Telephone number

If you can’t always find a copy of this magazine, help is at hand! Complete this form and

hand in at your local store, they’ll arrange for a copy of each issue to be reserved for you.

Some stores may even be able to arrange for it to be delivered to your home. Just ask!

If you don’t want to miss an issue

Subject to availability

✃

trough for easy dunking. With a precisiongrinder over-heating can be completelyavoided – fully machine the tool in itspre-hardened state, then grind only todress the cutting edges. In short, do theabsolute minimum of grinding, with barelydetectable feeds, like 0.001 inch, betweenpasses. Keep the temperature of thesurface you're grinding below 150˚F (65˚C),which is as hot as you can touch without(much) discomfort. Water dip frequently ifconvenient, air cool if not.

Use a diamond lap tohone the cutting edgesWhen making cutters from machinabletool steels like W1 and O1, do all theshaping you can – including edge grinding– before heat treating. This minimizesthe danger of softening a treated tool bygrinding after the fact. A hone is often allyou'll need to put on a working edge.

Remember, machinable tool steels arenot like HSS. O1 and W1 are very distantrelatives of High Speed Steel, really a

totally different material. For one thing,HSS is not machinable in the ordinarysense, so it has to be ground to thedesired shape. For another, it can beground to dull red temperature withoutaffecting its performance in the slightest– a good thing if you are trying to grind,say, a single point threading tool from a 3 ⁄ 8 inch square blank of M2. That would takeall day, possibly two, with the daintytechnique we have to use for O1 and W1.Grind HSS as aggressively as you like.Finally, no matter what you've readelsewhere, never cool HSS by waterquenching. It will likely be damaged by thethermal shock, and therefore more proneto failure in use.

Case hardening works, tooIf you are out of drill rod, and need aspecial tool this minute, you can oftendo the job by case hardening any steelyou happen to have on hand – 1018,even 12L14, whatever. A pound of casehardening powder goes a long way,which is good news in view of its cost.It is available from the usual specialtysuppliers such as McMaster Carr.Case hardened mild steel stands upto a surprising amount of use, but thehardened case is only a few thousandthsof an inch deep, if that, which means

practically no grinding. Much better isto fully machine the tool in its soft state;then, after hardening, sharpen it by aminimal amount of careful grindingfollowed by hand-finishing with an oilstone or diamond lap – just as you oughtto be doing with O1 and W1 steels. (In apinch, you can even dispense with thegrinding operation – go straight to the

stone or lap instead.) The great thingabout case hardening, compared to heattreating W1 and O1, is that it takes onlya matter of minutes, with no need fortempering: heat the workpiece to ‘brightcherry red’, dip it in the powder, reheat tothe same temperature, then quench. Justone caveat: make sure the work surface isevenly heated and uniformly covered withthe molten powder.

Is it worth all the trouble?Meaning, can tools made of W1 and O1deliver useful results? Absolutely. Here'sone example (photos 3 and 4) a specialpurpose 5 ⁄ 8 inch counterbore. Starting witha 5 ⁄ 8 inch rod of W1 (necked down to a ½inch shank), it was fully machined in asimple 20˚ milling fixture, leaving only afew thousandths of material to be groundoff in the sharpening process followingheat treatment. The pilot pin, a hardeneddowel, was installed after finishing.The tool shown here has survived fiveor six boring ops in 1018 steel withoutnoticeable degradation. ■

3

Counterbore from W1 steel.

Holes made

with the

tool.

Steel Metallurgy for theNon-Metallurgist

John D. Verhoeven, Iowa StateUniversity (Publisher: ASMInternational). Looks formidable butisn't; highly informative, easy to read.Available from Amazon.

Heat Treatment, Selection andApplication of Tool Steels

William E. Bryson (HanserPublications). This is not theWalk-in-the-Woods Bill Bryson.Available from Amazon.

Iron-Carbon Phase DiagramMSE 300 materialslaboratory proceduresDept. of Materials Science andEngineering, U of Tennessee, Knoxville

FOR ADDITIONAL BACKGROUND

4



8/10/2019 mew225


EXCLUSIVE

READER OFFER

1 Hardening, Tempering and Heat Treatment – Tubal Cain

2 Vertical Milling in the Home Workshop – Arnold Throp

3 Screwcutting in the Lathe – Martin Cleeve 4 Foundrywork for the Amateur – Terry Aspin

5 Milling operations in the Lathe – Tubal Cain 6 Measuring & Marking Metals – Ivan Law 7 The Art of Welding – W.A. Vause 8 Sheet Metal Work – R.E. Wakeford 9 Soldering & Brazing – Tubal Cain10 Saws & Sawing – Ian Bradley11 Electroplating – J. Poyner12 Drills, Taps and Dies – Tubal Cain13 Workshop Drawing 2nd Revised Edition

– Tubal Cain14 Making Small Workshop Tools – Stan Bray15 Workholding in the Lathe – Tubal Cain16 Electric Motors 2nd Edition – Jim Cox

17 Gears & Gear Cutting – Ivan Law18 Basic Benchwork – Les Oldridge19 Spring Design and Manufacture – Tubal Cain20 Metalwork & Machining Hints & Tips

– Ian Bradley21 Adhesives and Sealants– David Lammas

22 Workshop Electrics – Alex Weiss23 Workshop Construction – Jim Forrest & Peter Jennings24 Electric Motors in the Home Workshop

– Jim Cox25 The Backyard Foundry – Terry Aspin26 Home Workshop Hints & Tips

– Edited by Vic Smeed27 Spindles – Harprit Sandhu28 Simple Workshop Devices – Tubal Cain29 CAD for Model Engineers – D.A.G. Brown30 Workshop Materials – Alex Weiss31 Useful Workshop Tools – Stan Bray32 Unimat III Lathe Accessories – Bob Loader

33 Making Clocks – Stan Bray34 Lathework: A complete Course – Harold Hall35 Milling: A complete Course – Harold Hall36 Photo Etching – Brian King and Azien Watkin37 Dividing – Harold Hall38 Tool and Cutter Sharpening – Harold Hall

39 Model Engineers’ Workshop Projects – Harold Hall40 Bearings – Alex Weiss41 Grinding, Honing and Polishing – Stan Bray42 The Metal Workers’ Data Book – Harold Hall43 The Mini-Lathe – David Fenner44. The Metalworker’s Workshop 45. Basic Lathework46. Workshop Machinery47. Three-Phase Conversion48. Mini-Lathe Tools and Projects49. The Milling Machine

Online: www.myhobbystore.co.uk/WSP15Phone: 0844 848 8822 (Phone lines open: Mon-Fri 9am – 4.30pm)

Subscribers will receive an additional 5% saving if their subscription details

are correctly linked with their MyHobbyStore account. Prices are correct at

time of publishing. All prices are exclusive of P&P. Offer ends 01/03/2015.

Get All 49 Books For Just £245.00!

LIMIT EDT IME

OF F ER!

SA VE£144. 5 5 ! *

WORKSHOP PRACTICE SERIES



8/10/2019 mew225


23February 2015

No more than one prize with a value of £30 will be given each month. By entering you agree yourentry can be freely published and republished MyTimeMedia on paper or electronically and maybe edited before appearing. Unpublished tips may be carried forward to future months. You will beacknowledged as the author of the tip. There is no guarantee that any entry will be published and ifno publishable tips are received a prize will not be awarded. The decision of the editor is final.

Readers' TipsWe have £30 in gift vouchers courtesy

of engineering suppliers Chester

Machine Tools for each month's 'Top

Tip'. Email your workshop tips to

[email protected]

marking them 'Readers Tips', and you

could be a winner. Try to keep your

tip to no more than 400 words and a

picture or drawing. Every month wewill chose a selection for publication

and the one chosen as Tip of the

Month will win £30 in gift vouchers

from Chester Machine Tools. Visit

www.chesterhobbystore.com to plan

how to spend yours!

This month’s winning tip from Bob Reeve won’t leave you

gasping for air! He wins £30 of Chester gift vouchers.

1

3

2

The first runner up of 2015 is Adrian

Secrete. Many readers have discovered

the joy of tangential tooling, this tip

eases the height setting of these tools.

Adrian gets a Workshop Practice Series

book as a prize.

When using my tangential tool holder, to savetime setting the cutter tip height after sharpeningI made a simple jig.

The base of the jig is made from a permanentmagnet and the height of the column is made tosuit the recommended lathe cutting height.

After sharpening the cutting tool I place the jig onthe lathe bedway and the magnet holds it in place,I place the cutting tool into the holder and raise itup until it contacts the overhang of the jig thentighten the locking screw.

Adrian Secrete

As we get older we might expect toget a bit short of puff, but I didn’texpect that to apply to that useful littlegadget, usually known as a puffer(photo 1). These are inexpensive,available from several of our suppliesand might be replaced without asecond thought, but curiosity causedme to investigate why mine wasgetting short of breath. Photo 2 shows

the nozzle in close-up and the causeof the problem. During its workinglife the nozzle is in close proximityto mills, drills, saws and such like,sometimes getting a bit nibbled inthe process. A new nozzle could bemachined easily, but photo 3 showsmy solution which also improves theversatility of the device.

The 4mm push fit pneumatic fittingis inexpensive (available from MSCorder number CJN-00171L) and the 1 ⁄ 8 inch BSPT end is a push fit into therubber bulb without modification. Thedelivery pipe is easily replaced can bemade to suit the job in hand from anysuitable soft material that will notdamage the job or the cutter.

Why two puffers? Well, I actually

have three, one each for mill, latheand band saw. Why waste preciousworkshop time wandering aroundlooking for something that costs solittle? For me, unnecessarymovement is one of the SevenWastes in the home workshop justas much as in industry.

Bob Reeve



8/10/2019 mew225


›

Locator pin

for set-up

Tool heightto match

centre height

of lathe

Cross SlideBottom Dovetail Block

Top Slide

Tool Post

Cross SlideCentre of

rotation 60°

Top Slide32

Circular inset disc

in cross slide

Figure 1 - Assembled Top Slide & Toolpost

16

16

10

New locationfor clamp screws

Existing clampscrews

8 BA for locator pin

8mm dia hole 7mm

deep in underside

for location on the

cross slide disc

Holes M6 clear dia

counterbored 10.5

dia for cap screws

Bottom dovetail

block of top slide

8 BA

Locator pin

for set-up

3 dia

10 dia

2

6

4 dia 12 33.5

13.5

5

Figure 2 - Modifications to Dovetail Block also showing locator pin

25

Mini Lathe Ball Turning

February 2015

made. A suitable lever is also required ofreasonable length to enable the tool to behand swivelled against the blank to createthe spherical ball surface. In this case thelarge spanner provided with the ConquestMill has been adapted for this purpose butany suitable length of steel flat bar canbe used. Photograph 1 shows the generalset-up with an extended arbor holding agovernor ball blank ready for turning. Thelength of the handle ensures good controlunder hand action. Photograph 2 showstwo prepared ball blanks each with athreaded stud at the rear and centre drilledat the other end for tailstock support(more on this later).

Figure 1 illustrates the assembledmodified top slide arrangement and toolpost. It will be noted that the new holes inthe slide base block allow the top slide tobe set off to one side of the cross slidewith the rotation centre coinciding withthe existing circular inset disc which ispart of the cross slide mechanism. Detailsof the new holes required in the baseblock of the top slide are shown in fig. 2,

but note the recessed hole on theunderside to fit over the upstanding lug onthe top of the circular inset disc. There isalso a small threaded hole required in thebase block at the rotation centre of this toaccept a screw-in upstanding locator pin,tool tip high, which visually locates thecross slide position on the lathe centre lineand which can be used to also locate thecarriage location at the centre of the ballblank. The new tool post details are shownin fig. 3, hexagonal in plan shape, with aclearance cut away on one side where thisreaches its clockwise limit of rotation andcomes close to the projecting arbor. Thisallows the tool tip to reach closer to therear of the ball and produce a smallercollar. The dimensions of the hexagonalshape of the tool post shown is to suit thelarge spanner mentioned above but thiscan be adjusted to suit any other similarform of spanner including open endedtypes. So apart from the mounting holesand the height to the cutting tool, the restof the slide, tool post and leverarrangement can be whatever the userwishes or has suitable scrap box materialfor. Note that the modifications will haveentirely no effect on the normal use of thetop slide.

Initial Set-Up Procedure

The top slide has to be fitted onto thecircular recessed disc in the cross slideusing the cap screws through the newholes in its base making sure that thecentral hole on the underside fits neatlyover the upstanding lug of the disc.The screws must be tightened to clampthe top slide to the cross slide but onlyjust enough so that the top slide canbe rotated, albeit a little stiffly. Fit thelocator pin into the threaded hole andtighten down. With the ball blank securelymounted at the end of the arbor, thecross slide has to be adjusted to takethe rotation centre with its attachedupstanding locator pin across to thelathe centre line using the turned endof the blank or the tailstock centre as avisual guide for this and the cross slidelocked when centred. With the top slideset at right angles to the lathe axis, thecarriage is then adjusted to bring the tool

Fig. 1

Fig. 2



8/10/2019 mew225


Figure 3 - Toolpost & Mill Spanner Handle

35.5

35.5

60°

25 minimum

M10 postM6 cap

screws

Location of

cavity and

tool to suit

centre height

6

Mill spanner shown

but open end type

also suitable.

Starting position

shown relative to

lathe axis


tip in line with the end of the ball blank.From that position the carriage can beadjusted toward the headstock by half thediameter of the ball that it is intended toturn and the carriage locked. This then isthe starting position for turning the ballinitially using only light cuts. During theprogress of turning the ball it is necessaryto frequently check the tightness of thescrews holding the top slide to the crossslide. If these slacken too much, the radiusof swing becomes somewhat irregularcausing, vibration, chatter, poor finish anda possible dig-in.

Machining Procedurefor Governor BallsA particular problem with ball turningin this manner is the large amount ofclockwise rotation of the tool tip requiredto create the spherical surface and theresulting large outstand distance of the

arbor at its greatest overhang from thechuck, the first stage was to bring thetailstock centre into the end of the ballblank and proceed to turn only the rearhalf of the ball, remembering not to touchthe cross slide adjustment or the carriageadjustment, thus using only the top slideadjustment to advance the cut. This isshown in photo 3. The collar to be seen onthe rear of the ball is about 1 mm in depth.At completion of the rear half of the ball,the chuck jaws were released to allow thearbor with its half-finished ball to bemoved in much closer to the chuck andthe live centre replaced with a half centre.This second stage adjustment of the arborgives enough access to nearly finish theball and is illustrated in photo 4. Despitethe use of the half centre, the amount ofanti-clockwise swivel available to the tooltip in this position is a little limited by theclose presence of the tailstock so the outerend of the ball could therefore only bepartially finished to the limit of the toolclearance. It only remained at this pointthen to move the tailstock out of the way

to allow completion of the finishing cuts.Photograph 5 shows this final stage. It willbe appreciated by the reader that the useof the tailstock with its half centre whenthe ball is so close to the chuck is optionaldepending on how stiff the thin rearthreaded stud is to resist the cuttingforces. If the stud is thought to be stiffenough, it is possible of course to gostraight to the set-up shown in photo 5.The final outcome after a bit of polishing isshown in photo 6 and as fitted to thecompleted governor in photo 7.

Alternative Machining ProcedureA good alternative to the methoddescribed for machining the governorballs is to carry out the entire operationin one go by keeping the arbor at its fulloverhang from the chuck without tailstocksupport but giving it lateral and verticalsupport from a travelling steady. Since thecross slide is locked in position, the steadydoes not actually travel at all and simplyremains in the same position throughout.The general set-up for this is shown inPhotograph 8 which is for a much largersteel ball 24 mm in diameter. It will benoted here that I did not have a propertravelling steady to use for this and simplyfitted a brass v-ended flat to a reversed

ball from the chuck making the wholeset-up very non rigid and hence liableto producing chatter and a poor qualitysurface finish. To overcome this problemthere are three fairly obvious ways ofdoing it; 1) using a very stiff arbor ofsubstantial diameter at its full projectedoverhang from the chuck; 2) using amuch thinner arbor which is given lateralsupport using a travelling steady, and3) using tailstock support with a livecentre for part of the operation. There areadvantages and disadvantages with eachof these approaches which will becomeclear later when I look at both the secondand third methods in this article withsuitable examples.

For the purposes of the immediate needfor the governor balls, however, the thirdapproach described above was the oneadopted. This resulted in the turningprocess needing to be carried out in twodistinct and separate stages. With the

Fig. 3

43

Optional set-up for the 2nd stage to finish the ball with a halfcentre support.

Turning the rear of a ball.



8/10/2019 mew225


8/10/2019 mew225



I would like to think the photos are self-explanatory. Basically the jigs consistof a piece of alloy about 6mm thick,

two holes of the required size carefullydrilled adjacently on the centre line. Theshort bar, the guide, is pushed throughso that it will locate in the first holeof the chain. The longer bar has a 45degree point ground to the front end andhas been hardened. This bar is pushedthrough the alloy plate just far enoughfor the point to be easily visible (seephoto 3). When happy with the set up,I used a sharp punch to centre pop thealloy around the bars to fix them, Loctite

or super glue would do instead.I made three sizes just in case of a

need arises, 1 ⁄ 8 inch, 3 ⁄ 16 inch and 1 ⁄ 4 inch.In use they are a bit laborious butaccurate. Procedure is to drill the firsthole as accurately as possible on thescribed line, then put the jig into thehole and align the point on the line, atap with the hammer to mark the holeposition and then use a centre punchproperly to guide the drill bit. ■

Chain Drilling

Marker JigPeter Wilton offers a simple jig to ease the task of drilling a series of closely spaced holes.

1

3

2

A Chain Drilling Jig.

Chain Drilling MarkerSetting Up.

Three Chain Drill Markers.

Once in a while the need to drill a set of holes adjacent to each other occurs,

at least to me. More often than not it is to cut a flywheel blank from sheet of

steel or alloy. My bandsaws (yes, I have two elderly Burgess bandsaws, one

for wood and one modified for metal) are not very powerful and need a lot of

help coping with 1 ⁄ 2 inch or more steel so a set of pre-drilled holes does the

job. I hope that somebody is helped by this article.



8/10/2019 mew225



8/10/2019 mew225



8/10/2019 mew225


›

31February 2015

volts is reasonably safe compared to the

obvious hazards of 240 volts as long ascommon sense is used. The motor I usedhas three wires giving two speeds. Usuallythere are five wires with two of themgiving the 'Park' function for the wipers.When the wipers are switched off theykeep running until they reach their parkpoint at the bottom of the screen. It’s nottoo difficult to work out with a bit of trialand error. A multi-meter with a sounderfunction will find the two park switch leadsand these can be chopped off as they onlygo to a micro switch and are not neededhere. Using some power from a batteryor power supply the other leads can beconnected to find the best suited speed.Beware of the casing as this is normallythe earth and will spark if touched with thecables. The different leads go to differentwindings in the motor to give differentspeeds. Choose the speed and mark thecables used. If it suits use the casing and

With the gear cutting now

mastered, shown in the ModelEngineer April-May 2013 issue

(ref. 1), I could get on with building andfitting a motor to power drive the leadscrew. Although this is designed to fita Myford lathe, the idea could be easilyadapted to fit any lathe. The power comesfrom a car windscreen wiper motor. Theyare of course 12 volt dc which means a 12volt power supply will be needed. This canbe in the form of a battery, a transformeror a power supply. I picked up a 12 volt5 amp power supply off eBay for £5.00(photo 2). The motor itself could be foundon the same site, sourced from a scrapyard or salvaged from a car that is beingscrapped. They are all pretty much thesame with slight differences dependingon the make and model of car. As such Iwon’t delve into the wiring of the motorsas there are differences but they basicallywork the same. Playing about with 12

A Powered Lead Screwfor a Myford Lathe

Rich Wightmanand JulianHarrisoncombinetheir talents.

I wanted to power drive the lead

screw on my Myford lathe without

going to the trouble or expense

of fitting a stepper motor with

the associated electronics. I have

used 12 volt car windscreen wiper

motors and radiator fan motors on

other projects so I knew a wiper

motor would be powerful enough

and do the job nicely. It just needed

to be controlled in some way,forward and reverse plus variable

speed if possible. The mechanics I

could do myself but the electronic

side of things were a bit of a

mystery. My mate Julian looked

into it and said he could build a

controller that would give me the

required functions. Between us

we worked it out and built a veryuseful accessory. Photograph 1

shows the completed motor and

drive system.

The following article is how I

achieved it with the help of Julian.

As with most of my projects there

are no plans as such, as it was

a trial and error type of project

made up as I went along. It will be

mostly photos, but I will include a

few sketches.

12

The motor and drive system.

The switch- mode PSU.



8/10/2019 mew225



one cable but be aware this will push thelive into the casing first in one direction.If you have a ground earth on your lathethen this will earth the power. To avoidthis you will need to insulate the motorfrom the lathe which would mean usingplastic for the mounting bracket. It is mucheasier to use two of the cables. The cablesnot being used can be chopped or a betteridea would be to insulate them so theycan be used at a later date if you want toalter the higher speed. Another way toidentify the cables and switch is to removethe cover on the end of the gearbox andtrace the cables. Power will still be neededto check your choice of cable. I chose touse the faster of the two speeds whichturned out to be the right one to use formy lathe. It’s a simple matter to change 2wires if the slower speed is required butwith the variable speed controller I can goas low as virtually zero with a reasonabletop speed.

I used a 100 tooth 500mm long belt forthis project. The belts can be sourcedonline along with the gears if you don’t

fancy making them.The first job to be tackled was to make a

couple of gears. I chose to use a 40 toothgear on the motor and a 40 tooth gear onthe lead screw giving a 1:1 ratio. It was allexperimental so I had to take a guess atwhat gear sizes to use. As it turned out thegear sizes were a good choice. Both gears

are flanged. The flanges, 4 in all, are madefrom 1mm aluminium (photo 3) cut fromsheet and turned to size on a mandrel. Iturned them two at a time using the twogears to clamp them onto the mandrel.

The flanges on the hand wheel gear aresimply super glued on (photo 4), as thisone will be drilled and bolted to the handwheel while the gear on the motor has theflanges pop riveted on (photo 5). I’ll justshow one photos of the gear cutting here,for a full description please see myprevious article (photo 6).

5

7

6

8

Pop riveting a flange.

The leadscrew spacer.

Cutting the toothed core of a gear.

Counterboring the handwheel.

3

4

The unfinishedgear flanges,cut from sheet.

A finished ‘gear’ forthe toothed belt.



8/10/2019 mew225


›

.660

1.0

.1875

.1875

.375

.4375

33

Myford Powered Leadscrew

February 2015

important as the bore of the gear will bemachined to suit, (photo 10). Machine thebore of one of the gears to suit (photo11). Drill two 4mm holes through thehand wheel (photo12), and then fit the

counterbored (photo 8). The nut was thenmachined to suit (photo 9). The handwheel was then mounted on a mandreland turned down until a smooth finishwas achieved, the finished size is not

Fitting a gear to the motor was fairlyeasy. The motor has an 8mm threadedsection under which is a tapered splinedsection leading into the motor shaft. Borethe centre of the gear 8mm thencountersink, I used a large centre drill tocountersink which has a 60 degree anglesimilar to the taper on the motor. With acouple of drops of thread lock compoundthe gear can be tightened on to the motorshaft. The splined tapered section willbite into the aluminium gear and holdfirm. Fitting a gear to the lead screw

proved to be more of a challenge. I couldof course do away with the lead screwhand wheel altogether and just fit a gearin its place but I wanted to retain thehand wheel so that the lathe could beused in its normal manual fashion. Thehand wheel on a Myford is held on with aself-locking nut which is not fullytightened but used to adjust backlash.The hand wheel on my Myford latheneeded to be modified. There isn’t quiteenough room to fit the gear inboardwhich is where it needs to be to keep itout of the way and allow the lathe to beused manually. To gain a bit of room thehand wheel must be moved outwards. Imachined a spacer (photo 7), to thedimensions in fig. 1 which gave meenough room to fit in the gear but notenough thread on the lead screw to fit thenut so the hand wheel had to have somematerial machined away and

9 10

The modified leadscrew nut. Finish machining the handwheel.

Fig. 1

11 12

Boring a gear to fit the handwheel. Drilling gear fixing holes in the handwheel.



8/10/2019 mew225


To be continued...


gear and spot drill. Drill the gear tappingsize for 4mm. Remove the gear and tap4mm. (photo 13). Drill out the hand wheela clearance size for 4mm and countersink.Assemble the 2 parts with a couple of

countersunk socket heads screws, (photo14). A trial fit on the lathe to checkeverything clears ok (photo 15). Becausethe hand wheel is now further away Imade a new pointer (photo 16). It’scopied from the original, just a littlelonger and shaped so that I can removethe belt easily. After blacking a line ismarked then fitted to the lathe. Byslackening the screw it will tip up enoughto remove the belt (photo 17).

1. Model Engineer issue 4454, Volume210. Cutting Timing Belt Gears.Wightman, R.

REFERENCE

13

15

17

14

16

Tapping the gear.

A trial fit to check clearances.

The new pointer is easily moved to allow belt fitting.

Assembling the handwheel to the gear.

New and old pointers compared.



8/10/2019 mew225


Just a small selection from our current stock

• Telephone enquiries welcome on any item of stock. • We hold thousands of items not listed above.• All items are subject to availability. • All prices are subject to carriage and VAT @ 20%. • We can deliver to all parts of

the UK and deliver worldwide. • Over 7,000 square feet of tools, machines and workshop equipment.

tel: 01903 892510 • www.gandmtools.co.uk • e-mail: [email protected]

Opening times: 9am -1pm & 2pm – 5pm Monday to Friday. Closed Saturdays, except by appointment.

G and M Tools, The Mill, Mill Lane Ashington, West Sussex RH20 3BX

We NOW have a Brand New BUY ONLINE Website!Check it out at: www.gandmtools.co.uk

Myford Super 7 Lathe, Very Good Condition,

3ph, Tooled, £1750.00 plus vat.

Myford Super 7B, Excellent Condition, Tooled, 1ph,

£4250.00 plus vat.

Myford Super 7B, Little Used, Excellent Condition,

Well Tooled, 1ph, £5250.00 plus vat.



8/10/2019 mew225



knobs, tapped M4 and sealed with anO-ring. While building the first batch ofinstruments, I soon realised that theseemingly trivial operation of tappingdozens of knobs was taking adisproportionate amount of time andrisking a repetitive strain injury. Ofcourse, I could have built or purchased an

automatic tapping machine, but neitherthe time nor the cost required could bejustified, given that I was only strugglingwith making knobs! While repairing ourvacuum cleaner I noticed that eachthreaded hole in the plastic casing hadbeen engineered with shiny brass plugs,tapped to size and incorporated into themoulding. The result is a durable femalethread with much greater strength thanthe parent plastic, and which does notrequire any manual or machine tappingoperation in the factory. This pointed theway towards a solution to my problem.

When I dismantled (and re-assembled!)some other domestic appliances I foundthat these ‘threaded inserts’ are widely usedto create fastenings in items as diverse asmains plugs, TVs, printers and mobilephones (photo 3). More chunky versions arefound pressed into modern timber furniturewhere their purpose is to distribute the

My main hobby interest is the designand construction of scientificinstruments, in particular devices

for use in geophysical research. A recentproject was the construction of a sensitiveseismometer for detecting the microscopicground motion that results from distantearthquakes. The project was a success

and led to a small commercial venture in

Threaded Inserts

and other Hot TopicsMark Noel grows tired of tapping.

This article describes the use

of threaded metal inserts as a

speedy and economic alternative

to the tiresome manual creation

of tapped holes. These versatile

components are particularly

suited to the joining of plastic

and soft alloy components, and

are available in a range of sizes

and specifications to suit most

applications. The development of

a heated insertion tool (photo 1)

led unexpectedly to some other

gadgets, one of which has provedto be a welcome addition to my

chilly workshop this winter.

1

2

The heat staking tool in action. A set of brass M4 threaded inserts are beingheated and emplaced into a PVC component. The ATX power controller alsodisplays the stake’s operating temperature.

My VS1 seismometer which detects the sub-micron seismic wavesarriving from distant earthquakes.

which I now produce these instruments foramateur seismologists wanting to monitorthe shakes and quakes of the tectonic platesthat shape our world (ref 1 & photo 2).

The seismometer mechanism iscontained inside a clear acrylic cover thatprotects it from air pressure changes,dust and sudden fluctuations in

temperature. The lid is secured with eight



8/10/2019 mew225


›

37

Using Threaded Inserts

February 2015

stress at important joints. Most inserts aremanufactured in brass or steel and designedto be deployed as follows:

• Moulded In, by suspending the insertwithin the die during the injectionprocess. The domestic electric plugcontains an insert incorporated by thisprocess. Such inserts must be closed atone end to prevent flow of molten plasticback into the thread.

• Pressed in Cold, into a suitably sizedhole created by or after the mouldingor casting process. This is a lower-cost method that does not requiremodification to the injection mould.Suitable inserts can be open or closed,since blocking flow does not occur.

• Pressed in Hot, into a suitably sized holecast or drilled into the plastic moulding.This method is termed ‘Heat Staking’and requires a special tool that heatsthe insert in order to melt it into thecomponent. Of intermediate cost, thisprocess also permits changes to theinsert design without major modificationto an existing die. Suitable inserts canagain be open or closed at the inwardend, but if open, the staking tool needs toblock this aperture to prevent flow.

seismometer knobs in record time,changing what was previously a chore intoa fun task (photo 6).

Readers of this magazine will be veryfamiliar with the design of Myford andother small bench lathes, equipped with aquick-change toolpost and perhaps even atailstock turret. In contrast, the specialistlathes used to produce threaded insertsare designed for rapid tool changing andautomatic stock feed to permit fastturning, boring, knurling and chamferingto consistent and precise standards. Suchspecialised machines are unrecognisableto most home engineers and can achieve arate of production of from 7s to 25s perinsert, depending on the part’s size andcomplexity (photo 7). Making each insertgenerates similar or slightly more swarfthan the weight of the part itself, but allswarf is washed and together with thecutting oil is recovered for recycling.Occasionally Anchor even make specialbrass inserts with antique threads for therenovation of old Bakelite telephones.

Cold pressing of inserts is only appropriatefor compliant thermoplastics, such as PVCor ABS and not for brittle materials such asacrylic, or when the hole to be threaded isnear the edge of a part, risking a crack or

Threaded inserts are not a moderninvention but can trace their history backto the days of Bakelite telephones andswitchgear in the 1920s, when thisrevolutionary new plastic proved too weakfor tapping holes directly. Since then,inserts have found widespread use inindustry but are rarely used in ourworkshop projects. Trawling the internetfor a supplier of small quantities, I cameacross Anchor Inserts, a Britishmanufacturer with a huge catalogue thatextends over a wide range of thread sizes,lengths and materials, with a choice ofknurls, ribs and teeth to suit variousapplications (ref 2). I discussed myproblem with Anchor’s technical expert,Austin Wade, who kindly sent a selectionof M4 inserts to experiment with (photo 4).The final choice was the 7.9mm longAnchor model BW2015 which could bepressed cold into a 5.7mm diameter holedrilled in the seismometer’s PVC knobusing my 1 Tonne arbor press (photo 5).These brass inserts are machined with 4barbs on the circumference to resistpulling out, combined with a band of axialknurling to resist turning of the insert.Having made the decision, I purchased apack of 300 and completed a batch of

3 4

Examples of threaded inserts incorporated into variouselectrical appliances. Clockwise from top left: Mains plug,TV casing, desk clock, radio.

Examples of Anchor inserts. The BW2015 part on the left is theone used in this project.

5 6

Arbor press used to cold-press a threaded insert intoone of the seismometer’s PVC knobs.

A batch of seismometer knobs fittedwith M4 brass inserts.

more serious breakagedue to the forcesinvolved. In such cases

the process of heatstaking that wasmentioned earlier is thepreferred option. It isimportant to recognisethat this method canonly be used for theclass of materials termed‘thermoplastics’ (whichcan be remitted), asopposed to ‘thermoset’plastics which areformed from ingredientsthat react and fusetogether during the hightemperature mouldingprocess (and whichcannot be remelted). It isthis type of thermalstability which makesthermosets ideal formoulding kettles, plugs,



8/10/2019 mew225


To be continued...

R

R R

R R

R R

R R


maintain a set temperature. A suitablecomponent that can be obtained for zero orvery low cost is the ATX power supplyfound in desktop PCs. Despite theirelectronic sophistication, even a new 600Watt ATX unit can be bought for under £20

and they can even be salvaged free fromyour local amenity site or computer repairshop. I extracted an Enlight ATX unit froma broken Windows 95 computer, reckoningthat the 150 watt output would be ample toraise the heat stake to a sufficienttemperature (photo 8).

heat staking tool it is important to note thatsome plastics give off hazardous fumes

when heated and so provision should bemade for operation in a well-ventilatedspace. The risks associated with heatingcertain plastics are detailed in ref 4.

Glancing at the table above, it can beseen that most thermoplastics we are likelyto handle have transition temperaturesbelow about 130 degrees C, with onlyacetal and polycarbonate requiring a muchhigher value. However, since thesematerials are actually chosen for theirtoughness, they are unlikely to really needa threaded insert fastening, and I thereforedecided to exclude these higher transitiontemperatures in the tool’s specification. Sowhat heat source should we use? A gasburner offers power but lack of fine control,leaving an electrical heater as the idealcandidate. Rather than dismantling mywife’s hair dryer in the search for suitablewire, I decided that the more harmoniousapproach was to purchase a set ofaluminium-bodied power resistors with ahigh temperature rating and mount theseon a solid block of brass to form a compactheat source. Such resistors are flanged forchassis-mounting, are relativelyinexpensive, and can be found rated to atemperature of 200 degrees C, which suitsthis project perfectly. For a supply of V volts, connected to a resistor of value R ohms, the power dissipation is V2/R wattsand the current through the component is

simply V/R amps. An array of identicalresistors each of R ohms, can be wired incombinations of serial and parallel suchthat the total resistance is still R, whileincreasing the power dissipation (fig 1). Ofcourse, we still need a power supply ableto drive current through the resistor array,and one which must be controllable to

hairdryers and other hot appliances. As youcan imagine, heat staked inserts are more

intimately bonded to the host part andtherefore can sustain greater loads in afinished assembly. I have a number ofprojects planned in my workshop where thiswill be a requirement, and so I decided todesign my own heat staking tool. As theproject developed it diversifiedconsiderably, eventually resulting in twomore devices which have proved valuableadditions to my workshop. As ever, I havetried to keep the cost to a minimum and touse recycled parts wherever possible.

The Heat Staking ToolThe main purpose of this tool is to holdand then heat the threaded insert to asufficient temperature that it enters thepilot hole with little force, while plasticflows into the flutes and knurls to completethe bond. Hence, key requirements arethe means of raising and monitoring thetemperature, and guiding the insert intothe hole. I decided to limit my ambitionsby using my existing pillar drill to drive theinsert, leaving only the problem of heatingthe insert and measuring the temperature.In this context the figure of interest is the‘Glass Transition Temperature’ or Tg for thethermoplastic, which is the point at whichthe material softens to a rubbery state,rather than fully melts to a liquid. Valuesof Tg for the common engineering plastics

which we generally encounter in ourworkshops are listed in table 1.

Figures for a comprehensive list ofplastics are given in ref 3. Beforeembarking on the construction of your own

7 8

The automatic lathe used by Anchor Ltd for the productionof threaded inserts.

The Enlight 150 Watt ATX power supply used in this project.

Table 1

MATERIAL Tg, ˚C (approx.)

ABS 110 - 125

Acetal 175 - 185

Acrylic ~ 110

Nylon 40 - 60

Polystyrene 90 - 110

Polythene 70 - 80

PVC 65 - 85

Polycarbonate 140 - 150

Fig. 1

Various methods for connectingarrays of resistors, each of R Ohms,into parallel-series combinations,such that the resultant resistance isstill R Ohms.

1. The VS1 seismometer is built to order by Rockwave: www.rockwave.co.uk2. Anchor inserts manufacture and supply a vast ranges of metal inserts. The minimumpack quantity is about 100 parts. For further details visit: anchorinserts.co.uk3. A comprehensive list of transition temperatures for a wide range of polymers isprovided by Perkin Elmer at: www.perkinelmer.com/CMSResources/Images/44-74863TCH_MPTGAndStructureOfCommonPolymers.pdf 4. The hazards of fumes released when plastics are heated are documented by the UK’sHealth and Safety Executive at: www.hse.gov.uk/pubns/pps13.pdf

SUPPLIER REFERENCES



8/10/2019 mew225



8/10/2019 mew225



As a tribute to the man who designedthe machine a group of us havecompiled a document set to enable

anyone to reproduce the machine. Somepeople, recognizing the uniqueness of thedesign have produced a set of castingsfor the major components. Others haveadapted the design to develop their ownmodern version of the machine (e.g. AlanJackson’s Stepperhead).

History of the design, drawingsand manufacturing notes.Originally conceived in the early 1950sby David Urwick, the design was welldocumented at the time and revisions

that not always do the fastest win the racenor the mightiest win the battle, wesubmit these manufacturing notes for theUrwick machine for anyone’s scrutiny sothey can utilise some of David’s ideas ormake a replica of the machine themselves.

The orthodox method of making the

patterns for the castings might beprohibitive. The use of expandedpolystyrene as expendable patterns using ahot knife or 3D CNC might be the way to go.

Descriptions and images of the MetalMaster (Impetus) and Labormil are on thewww.lathes.co.uk website.www.lathes.co.uk/metalmaster/ andwww.lathes.co.uk/labormil/

Articles about the Metal Master andsome of its machine elements written byDavid Urwick appear in these editions ofModel Engineer .

A Free- Lance Lathe 1st March 1951

A Revolutionary 4th January 1974

A Keyway Breakthrough 15th August 1980

METALMASTER - A ZeroTaper Machine Tool 2nd July 1982

made resulting in the hand drawnmanufacturing set included with thesenotes was finalized in the 1980s.

Unfortunately, information, materialsand documentation related to sporadicdocumentation efforts have appeared anddisappeared on a number of websites over

the past dozen years or so. It is hoped thatby pulling the various sources ofinformation together and giving it somestructure we may encourage more to havea go at making and building this trulyunique machine.

The design was certainly revolutionaryand it was used as a basis for the largerLabourmil machine. That machine wasmarketed for the small jobbing machineshop or as a millwright’s machine tool.

On that basis the Urwick Metalmasterwould be an ideal machine for the modeland experimental engineer. However,things mostly never turn into an idealsolution without luck, money andpersistence. Dyson had to fight to ensurehis designs weren’t either rubbished orstolen by others.

Urwick included in his machine manysimple ideas that should have put it at thetop of its chosen market. So remembering

The Metal Master

(Impetus) Machine ToolMike Philpotts introduces an unusual multipurpose machinetool in an article which accompanies a detailed set of plans tobe found at www.model-engineer.co.uk/metalmaster

Once in a while someone designs

something really innovative

which at first sight you could

think would take the world

by storm. Sadly because of

entrenched viewpoints, vested

interest and maybe a lack of

marketing skills such good

ideas do not always achieve the

recognition they deserve.

The Metal Master (Impetus)machine tool by David Urwick is

one such innovation. It is still not

clear why this idea did not take

off. The machine is ideal for the

small home machinist workshop

and would avoid the somewhat

larger investment in cash and

the space required for multiple

machines to achieve the samemanufacturing capability.

The original Metal Master Machine Tool.



8/10/2019 mew225


41February 2015

Mick Collins, who bought David’s ownoriginal machine, agreed with DavidUrwick’s widow that the drawings shouldbe made public and that each user of the

drawings would make a small donation toher for doing so. It is not clear how thedonation was to be made for this‘shareware’ or ‘Open Source’ material. Ithas been agreed that, unless a relative ofDavid Urwick can be found, anyone usingthe drawings will be invited to make adonation to REMAP, MEW’s sponsoredcharity. Full details are with the drawings atwww.model-engineer.co.uk/metalmaster

A member of the Metalmaster yahoogroup re-created the core set of drawingsas 2D DXF files and posted them for thegroup. Another member of the group

11) Hollow mandrel passes ¾ inchstock bar.

12) No 3 morse taper nose acceptslarge collets.

13) A boring and facing head with autofeed can be used as in full scalehorizontal boring practice.

14) An extra deep jawed machine vicecan be used in view of the freedomof vertical movement and endmills, flycutters and slitting sawsused as with a horizontal millingmachine.

15) The machine can be used as ahand shaper for cutting keywaysetc.

16) A special simple screwcuttingsystem is used, providing a rangeof threads with elementary trainsand a selection of metric thread toreasonable tolerance accuracy, also19TPI.

17) The use of a single dog clutch onthe mandrel makes it impossible topick up the wrong thread.

18) The accuracy of parallel turning

is under control of the operator -the bed is adjusted to ‘zero taper’condition.

19) A dial test indicator (DTI) mountedon the auxiliary bed is, at all times,available to check and align workin the machine.

20) The entire machine can be readilydismantled into manageablepieces, put in the back of an estatecar, and reassembled elsewhereready for work, very quickly.

■

made expanded polystyrene patterns toenable a set of castings to be made by thelost foam process. Some of those imageshave been included online to assist withvisualization. Another member of thegroup created the text files of DavidUrwick’s notes and they are included also.

Metal Master unique featuresMetal Master Machine Tool uniquefeatures identified by W. D. Urwickare listed below.

1) Vertical movement of the bedbenefits all operations.

2) Machine will swing 8.00 inchesbetween centres or 14.00 inchesover bed with tailstock andauxiliary bed removed.

3) Back feed tailstock will pass rightover saddle - no overhang.

4) Tailstock fitted with zerosetting depth gauge.

5) Pulley / Flywheel / Hand wheel

11.00 inches diameter serves asa 60 hole dividing head with sub-divisions to 360 degrees.

6) Large slotted work table 10 x 4.5 x7.5 inches cross travel.

7) Large indexing dials (3 and 3.5inch diameter) to cross slide andleadscrew.

8) In normal use a 4x4 tool post isused without top slide. No packingof tools is necessary.

9) Top slide for short tapers only.10) Taper turning between centres for

full travel of the saddle.

David Urwick's Metal Master

A rendered 3D model of the Metal Master.

Some recently produced Metal Mastercastings from the new 3D model.



8/10/2019 mew225


MODEL ENGINEERS’

Subscribers, see these adverts five days early!

S U B S C R I B E T O D A Y

A N D S A V E £ £ £ ’ S FREE PRIVATE ADVERTS

YOUR FREE ADVERTISEMENT (Max 36 words plus phone & town - please write clearly)

Town:

Please use nearest well known town

Date:Phone:

NO MOBILE PHONES, LAND LINES ONLY

SEE MORE ITEMS FOR SALE AND WANTED ON OUR WEBSITE www.model-engineer.co.uk/classifieds/

NO NEED TO WAIT – PUT YOUR OWN FREE CLASSIFIED ADVERTISEMENT ON OUR WEBSITEwww.model-engineer.co.uk/classifieds/

Machines andTools Offered■ Myford ML7B, retrofitted

clutch unit and Top/Cross Slidedial. 3-Jaw and (new) 4-jawand drill chucks. Four-way toolpost. Older machine, smoothrunning on newish (old stock)Brook Gryphon 1-phase motor,Dewhurst and NVR switching.£800 O.V.N.O.T. 01642 886980.Stockton–on-Tees.

■ Quantity of hand and machinereamers, slitting saws and taps.Second hand and new. Ringfor details. £200 plus post andpacking or buyer to collect.T. 0208 6414238. Surrey.

■ CNC Dugard Dyna MyteMiller £450. Edgar lathe 18 inchbetween centres. Gap bed 5 inch.£350. Buyer collects.T. 01650 521244.Newtown, Powys.

■ Portass 31 ⁄ 2 inch bench latheBGSC, 3 chucks, turning andboring tools. £210. Chester

Conquest bench miller, 3MT,selection milling and facingtools. £350.

T 01423 505425.

■ Lathe Keighley Lift 5 x 16inch. Three jaw and 4-jawchuck, change gears. Old butserviceable £150 O.N.O. Buyercollects. Stripped for transport.T. 07968 018986.Southend on Sea.

■ Chester DB10G centre lathe250mm swing, 550 betweencentres. 3MT tailstock, metric &imperial thread cutting. Singlephase motor. Complete with3-jaw, 4-jaw, faceplate, travellingsteadies, drill chuck etc. £800.

T. 01652 653697.Scunthorpe.

Materials and Fixings■ Titanium bolts. Large caphead (Allen) grade 5 titaniumbolts 160 x 20mm threaded25mm metric coarse, plus nut.T. 01674 676740.Montrose.

Models Offered■ 5 inch Britannia locomotiveand tender. Fully certified.

Harrogate show winner 1999.Little use due to poor health.T. 01325 377763.Darlington.

■ 7¼ inch class 08 petrolhydraulic loco. Little used, goodcondition. £3500 O.V.N.O.T. 01562 60658.Kidderminster.

Books and Periodicals■ Engineering In Miniaturemagazines 1986,1987,1988,1993,1994,1995,1996,2001. Totals 96

(approx.) copies. £25 O.N.O.T. 01452 883417.Gloucester.

■ Model Engineer February 26 –1953 to January 17 – 2008 only22 magazines missing. Bundledby year in files. 1202 copies, alsoindex 1975 to 1992. Offers.T. 017683 71642.Penrith.

Kits and Castings■ Thirteen castings and book forMark One Quorn Grinder £75.

Buyer collects.T. 0208 959 1443.N.W. London.

Wanted■ Small gas or electric furnacesecond hand. T. 02920 308234.Cardiff.

■ Exchange 89 key V.B. scalefairground organ, new 1998,plenty of music. Exchange forlarge model traction engine orsimilar. What offers?

T. 0121 5013190.Birmingham.

■ Harrison L5 spares orcomplete machine for spares –and steadies.T. 01642 321537.Middlesborough.

Adverts will be published in Model Engineer and Model Engineers’ Workshop.

The information below will not appear in the advert.

Name ...........................................................................................................

Address .......................................................................................................

....................................................................................................................

....................................................................................................................

................................................................ Postcode .....................................

Mobile....................................................... D.O.B. ........................................

Email address. ..............................................................................................

Do you subscribe to Model Engineer ❑ Model Engineers’ Workshop❑

Please post to:ME/MEW FREE ADS, c/o Neil Wyatt, MyTimeMedia Ltd,Enterprise House, Enterprise Way, Edenbridge, Kent TN8 6HFOr email to: [email protected]

Photocopies of this form are acceptable. Adverts will be placed as soon as space is available.

Terms and Conditions:PLEASE NOTE: this page is for private advertisers only. Do not submit this form if you area trade advertiser. If you wish to place a trade advert please contact Duncan Armstrong on01689 899212 or email [email protected]

By supplying your email/ address/ telephone/ mobile number you agree to receivecommunications via email/ telephone/ post from MyTimeMedia Ltd. and otherrelevant 3rd parties. Please tick here if you DO NOT wish to receivecommunications from MyTimeMedia Ltd: Email ❑ Phone❑ Post❑ or other relevant 3rd parties: Email❑ Phone❑ Post❑

❑WANTED ❑FOR SALE




8/10/2019 mew225


New additions to the Polly loco range:

5” gauge 0-4-0 Saddle Tank ‘Trojan’ & ‘Prairie’

POLLY coal fired kit build 5”

gauge locos are renowned for their

ease of construction and reliable

performance on the track.

Retaining all these strengths, the

new additions bring more of a

scale appearance to these

wonderful locos. Ideal

construction projects for novice or

experienced builder.

‘Trojan’, based on the proven

Polly I mechanics, produces a

good likeness of the attractive

little loco based at the Great

Western Society, Didcot.

Our new ‘Prairie’ is the logical

development of our very popular

Polly V large tank loco. Again

incorporating proven mechanics

and boiler, this model can be

customised to provide a likeness

of a full size GWR tank

locomotive.

These semi-scale models bridge

the gap between our classic Polly

kit locos and the fine scale modelsof our Practical Scale range. With

the option to add further cosmetic

detail, these models can be

displayed with pride in the

knowledge that on the track, their

performance is second to none.

For more details of these and other Polly locomotive kits, visit our website or see our catalogue.General catalogue including supplies and fine scale locos £2 posted (UK) Kit Loco Catalogue £3




8/10/2019 mew225


N o . 2 2 3

D E CE MB E R 2 0 1 4

T H E E S S E N T I AL MAG AZ I N E F O R E V E R Y H O B B Y E N G I N E E R

£ 4 . 2 0

E NGINEER INGGRO UP

MO D E L E N GI N E E R E X H I BI T I O N 20 14 S H O W GU I D E I N S I D E !

J oi n t he c onv e r s at i on about t hi s is s ue : w w w .m o d e l - e n g i n e e r.c o .u k

COV ER FE AT UR E

P r e ci si o n Mi l l i ng V i ce P l ans & D e t ai l s o f Mi k e C he ck l e y ’ s C o mp act D e si gn

F O C U S O N MI L L I N G H i gh S p e e d S p i nd l e Ad ap t o r Al i gni ng a Be ncht o p Mi l l S e l f -R e l e ase D r aw b ar

Mi l l i ng o n an ML 7

1907 - 2 0 1 4

w w w.m o del en gin ee rsh ow .c o.u k

1 2-1 4 De c em be r 20 14 S an do w nP ar kR a c ec o urs e

O P

EN IN G H O U R

S Fr i d a y

, 1 2t h a ndSa tu

rd ay, 1 3 t h

1 0.00am

-5.00 p m

(La stad mi s s

i o n: 4.00 pm)

S unday,

1 4th 1 0. 00 am-4.0

0pm (Lastad m i s si on: 3

. 00p m)

■ C ompe t

i t i on Cl asses

■ F r e e SM EE

Lect ur es ■

Wo r k shop De

mon st r ati o ns ■ T

rade S t ands

■ C l u bs & S

oci et i es ■ M e et

t he M a kers !

S HO W G U ID E

F R E E

F RE E V I N T AG E W O RK SH O P P RI N T

ME C ov er.i nd d

0 5/ / 0 4 0:4

SUBSCRIBE TODAY

CARD PAYMENTS & OVERSEAS

Mr/Mrs/Miss/Ms ....................Initial ...........................Surname ..................................

Address ......................................................................................................................

.....................................................................................................................................

Postcode ................................................... Country .................................................

Tel ............................................................................. Mobile ......................................

Email .......................................................... D.O.B ....................................................

Mr/Mrs/Miss/Ms ....................Initial ...........................Surname ..................................

Address ......................................................................................................................

.....................................................................................................................................

Postcode ................................................... Country .................................................

Postal Order/Cheque Visa/MasterCard MaestroPlease make cheques payable to MyTimeMedia Ltd and write code V685 on the back

Cardholder’s name........................................................................................................

Card no: (Maestro)

Valid from............................... Expiry date.................... Maestro issue no....................

Signature.................................................................................. Date............................

Originator’s reference 422562

Name of bank ...............................................................................................................

Address of bank ..........................................................................................................

.....................................................................................................................................

..................................................................................Postcode ..................................

Account holder ............................................................................................................

Signature ....................................................................................... Date ....................

Sort code Account number

Instructions to your bank or building society: Please pay MyTimeMedia Ltd. Direct Debits fromthe account detailed in this instruction subject to the safeguards assured by the Direct Debit Guarantee.I understand that this instruction may remain with MyTimeMedia Ltd and if so, details will be passedelectronically to my bank/building society.

Reference Number (official use only)

Please note that banks and building societies may not accept Direct Debit instructions fromsome types of account.

SUBSCRIPTION ORDER FORM

POST THIS FORM TO: MODEL ENGINEERS’ WORKSHOPSUBSCRIPTIONS, TOWER HOUSE, SOVEREIGN PARK,MARKET HARBOROUGH, LEICS LE16 9EF.

Please visit www.model-engineer.co.uk/terms for full terms & conditions CODE V685

DIRECT DEBIT SUBSCRIPTIONS (UK ONLY)

Yes, I would like to subscribe to Model Engineers’ Workshop

Print + Digital: £12.75 every 3 months(SAVE 23% on shop price + SAVE 75% on Digital Download + FREE GIFT)

Print Subscription: £10.50 every 3 months (SAVE 23% on shop price +FREE GIFT)

YOUR DETAILS MUST BE COMPLETED

PAYMENT DETAILS

I WOULD LIKE TO SEND A GIFT TO:

INSTRUCTIONS TO YOUR BANK/BUILDING SOCIETY

Yes, I would like to subscribe to Model Engineers’ Workshop,for 1 year (13 issues) with a one-off payment

TERMS & CONDITIONS: Offer ends 27th February2015. MyTimeMedia Ltd & Model Engineers’ Workshopmay contact you with information about our other products and services. If you DO NOT wish to becontacted by MyTimeMedia Ltd & Model Engineers’ Workshop please tick here: ❏ Email ❏ Post ❏ Phone.If you DO NOT wish to be contacted by carefully chosen 3rd parties, please tick here:❏ Post ❏ Phone. Ifyou wish to be contacted by email by carefully chosen 3rd parties, please tick here: ❏ Email

HURRY

OFFERCLOSES27th FEBRUARY

2015

PRINT + DIGITAL SUBSCRIPTION

PRINT SUBSCRIPTION

Free Book: Miniature InternalCombustion Engines*

13 Issues delivered to your door

Save up to 23% off the shop price

Download each new issue to your device

A 75% discount on your Digital Subscription

Access your subscription on multiple devices

Access to the Online Archive dating backto Summer 1990

Exclusive discount on all orders at

myhobbystore.co.uk

Free Book: Miniature InternalCombustion Engines*

13 Issues delivered to your door

Save up to 23% off the shop price

Exclusive discount on all orders at

myhobbystore.co.uk

UK ONLY:

Print + Digital: £53.50 (SAVE18% on shop price + SAVE 75%on Digital Download + FREE GIFT)

Print: £44.50 (SAVE 18%on shop price + FREE GIFT)

EUROPE & ROW:

EU Print + Digital: £61.95EU Print: £52.95

ROW Print + Digital: £61.95 ROW Print: £52.95




8/10/2019 mew225


D I G I T A L

S U B S C R I P T I O N S

A V A I L A B L E O N L I N E !

SUBSCRIBE SECURELY ONLINE CALL OUR ORDER LINE

www.subscription.co.uk/mewl/V685 0844 543 8200Lines open weekdays 8am – 9.30pm & Saturday 8am – 4pm

BT landline calls to 0844 numbers will cost no more than 5p per minute. Calls from mobiles usually cost more.

Quote ref: V685

TERMS & CONDITIONS:

Offer ends 27th February2015. *Gift for UK Print or Print + Digital Subscriptions, while stocks last.**When you subscribe by Direct Debit. Please see www.model-engineer.co.uk/terms for full terms & conditions.

SAVE23%** ON THESHOP PRICE &75% ON DIGITAL

Miniature Internal Combustion

Engines by Malcolm Stride

Model engineers have been makingmodels of internal combustion engines

since the invention of the real thing,

but it has always been surrounded by

a mystique and a perceived difficulty

that has put many people off.

This book by Malcolm Stride is

a great guide to the techniques

involved in producing all the

components required to build amodel internal combustion engine.

Collected together is sufficient

information about a variety of

engines and the

relevant design

and construction

techniques to

assist prospective

builders to

produce a

working model

I/C engine.

Miniature Internal

Combustion Engines*

when you subscribe today

Receive a FREE BOOK:W O R T H £ 19 .9 5



8/10/2019 mew225


Ø37.0

1 4

Ø29.0 PCDZ

Z

A

Ø 1 2

0.5 x 45°(Typ 4 pls)

4.0

6

Section Z-Z

Ø4.5

= 8 =

Detail AScale 4 : 1


Clamp ring (fg. 8)The clamp ring performs the duty ofholding the leadscrew nut in place anddoes not require any great accuracy toperform its function.

Chuck some mild steel bar in the lathe.Face and turn the OD, ID as per the drawing.Add chamfers or just debur to remove sharpedges and part off to the correct width. Thedimensions are not critical but follow thedrawing to avoid any interference. Clampthe ring on to the bed of the milling machineelevated using washers to allow for drillingthrough the part. Centre the milling spindleon the centre of the clamp ring and drill thefive clearance holes. Using the same holecentre location machine the slots to providea recess for the socket head cap screws(photo 21). Finally mill a flat on one side ofthe clamp ring so it sits nice and flush withthe moving jaw.

Support Plate (fg. 9)The support plate resists any rotationof the moving jaw when clamping aworkpiece. As the leadscrew is situated

below the point at which the clampingforce is applied there will always be amoment generated rotating the jaw.

All we need for the support plate tofunction properly is one smooth surface.Machine the plate to size leaving thethickness slightly oversize. Then, using theflycutter machine the thickness down tosize (photo 22). The thickness isn’t criticalbut a nice smooth surface helps the platerun smoothly against the top face of the Tslot machined in the base.

Mark up the plate with its finaldimensions and using the edge finderlocate the mill spindle on to the edge ofthe plate. Using your measured dimensionadjust the dimension from the hole to theedge to ensure the hole pattern is in thecentre of the plate. Drill and counterborethe four holes as per the drawing (photo23). Add chamfers or deburr all around theplate to remove the sharp edges.

grooved in one of the jaws in both thehorizontal and vertical direction for theclamping of round bar.

To improve the accuracy of the jaws Idecided to use ground stock as this

material is parallel and machined tooverall size. All that is required is for thematerial to be cut to the desired length.The length isn’t critical but it is desirableto have them both the same. Once cut tolength measure the final size of the jawsand adjust the dimensions from the holeto the edge to get the two holes centre onthe jaw (photo 24). Drill the holes as perthe drawing and repeat the process forthe second jaw.

Vice Jaws (fg.10)Making our own vice jaws provides acustomizable feature of the vice for theclamping of different shaped workpieces.I decided to incorporate a V shaped

Michael Checkley shows how you can make a solidand practical tool that also looks good in the workshop.

A Precision

Machine ViceDesigning and building a vice gives the opportunity for many personalised

features to be incorporated in the design including mounting features for

different vice orientation; endstops; and a variety of custom vice jaws forclamping different shaped parts.

Part 3

Fig. 8



8/10/2019 mew225


›

12.5 36.0

1 1 .

0

2 8 .

0

14.5 32.0

4 x Ø5.5 thru all Ø10 5

5 0 .

0

7.0

61.0

0.5 x 45°(Typ 8 pls)

9 .

0

12.056.0

2 x Ø3.3 6 M4 x 0.7 - 6H 4

2 0 .

0

0.5 x 45°

10.0

80.0

Precision Machine Vice

47February 2015

Vice assembly (fg. 11)This is the stage where the parts arecarefully aligned and shimmed to ensuresmooth operation.

Bolt the support plate to the moving jawand check how smoothly the moving jawslides along the vice base. Mine was tightso I shimmed the support plate with asingle layer of aluminium foil whichallowed the jaw to move freely with noundesirable ‘wobble’. Locate theleadscrew nut in to the moving jaw andsecure in place using the clamp ring. Atthis stage tighten the screws finger tight. Ifthere is any movement of the nut in thebore then a few operations of the vice willhelp the nut to find its best position andthen the nut is clamped in place. Securethe collet to the leadscrew and wind theleadscrew in to the nut (photos 25 & 26).

21

23

22

24

Milling the counterbore slots.

Drilling and counter-boring the holes.

Machining the plate to the desired thickness.

Mark out the holes from the referenceedges and drill the holes.

Fig. 9

Fig. 10



8/10/2019 mew225



Secure the leadscrew bush in placewithin the fixed jaw and mount the fixedjaw on to the vice base securing with fourM5 screws. Again, these screws shouldonly be tightened finger tight as a fewoperations of the vice will align the parts.

Fit the finger grip knob and secure usingthe M5 screw and two M4 grub screws.Operate the vice a few times lubricatingthe sliding faces with slideway oil. Tightenall the fasteners.

Secure each jaw in place using two M4screws. There are no features on the jawsto ensure they are sitting square so thesewill have to be ‘clocked’ for square everytime they are removed and replaced.Alignment features such as dowels couldbe included in the design if one desired.

Finishing the partsHow much effort is put in to this stage isentirely the choice of the builder as thiswill not affect the performance of the vicebut will make the vice a more desirabletool to use and gives the vice a moreprofessional look.

I decided to paint my vice as I feel itgives the vice a more finished andprofessional look but the vice could havestayed as bare metal. Emory cloth on asurface plate will quickly removemachining marks but can just as quicklyround off edges and corners ruining (inmy opinion) the finished look of a part. Iwould therefore recommend that anyheavy emory cloth work is done beforechamfers are added to achieve nice welldefined corners.

Once happy with the surface finish ofthe machined parts I masked off allmating surfaces and internal surfaces andsprayed each part with an acid etchprimer (photo 27).

25

27

26

28

The fixings and some small parts.

Masked base sprayed in primer.

Leadscrew assembled in to fixed jaw.

Moving jaw withfinal green paint.

Fig. 11



8/10/2019 mew225


Precision Machine Vice

49February 2015

29 30

Finished components assembled. Milling steps in the jaws.

Two coats of primer gave good coverageand a smooth surface. Following theprimer I then gave three coats of topcoat,

enamel based Plasticote (photo 28). I’mstill undecided how resistant this paint isto cutting fluids so proceed with this paintat your own risk! It hasn’t come off yet butI’m sure there are better paints out there

that would give a more lasting finish(photo 29).

Once assembled I decided to machine a

step in the jaws for holding a low profileworkpiece (photo 30). Clamp a parallel inthe jaws to hold the moving jaw firmly inplace and machined a 3mm x 3mm step ineach jaw.

This vice design allows plenty of scopefor customisation. For those that wouldbenefit from new drawings with their

features added then please feel free toemail [email protected] and Iwill do my best to provide updateddrawings. ■

DON'T MISS THIS GREAT ISSUE - SEE PAGES 16 AND 45 FOR OUR LATEST SUBSCRIPTION OFFERS

In our

Next Issue Coming up in issue 226

On Sale 27th February 2015

› ›

› ›

› ›

Inchanga recounts twenty yearswith an imported milling machine

Mike Haughtondetails twolathe carriagelocks

John Ashtonfits a Quick

Change Toolpostto his lathe




8/10/2019 mew225



8/10/2019 mew225


›

51February 2015

The Hobbymat MD65 was a brightyellow East German mini-lathe(specified as 65mm swing and 300mm

between centres), sold in the late ‘80s untilthe Berlin Wall came down, and I boughtmine new in August 1990 for £410. Likemany Soviet bloc products, the detailing

was less than perfect, but the machineis solid (45kg) and the fundamentals aregood, putting many contemporary lathes toshame. My machine came in an expandedpolystyrene box that fitted in a hatchbackcar boot, and was very well tooled asstandard, including:

• 80mm three jaw self-centring chuckwith standard and reverse jaws

• MT2 headstock dead centre• MT1 tailstock live and dead centres• 10mm Jacobs-type drill chuck• Terrible tool post• Twelve change wheels: 20, 30, 35,

40, 50, 55, 60, 60, 65, 70, 75, 100• Right angle plate• Small vice to allow light milling• Appropriate spanners, hex keys,

and screwdriver• Operating Instructions and Spare

Parts List (48 page yellow booklet)• Supplementary Notes by Peter Jones

(12 page yellow booklet)

I bought the lathe because my mainhobby interest is audio and the SMESeries V pick-up arm had just appeared.However, the SME was £1200 (a lot now,let alone in 1990), so I figured that even ifa lathe plus accessories reached £1000,that was still cheaper than the SME V, andI’d have a lathe left over at the end.

passes through a pre-existing hole in thelathe bed to the power switch. Unlike thelocal fluorescent, I have mixed feelingsabout the spot lamp as it tends to foulfingers when tightening drills in thechuck. The light and lathe plug into asemi-permanent four outlet extensionlead hung on the wall clear of the swarfzone and allow a vacuum cleaner to beeasily plugged in.

As the lathe only weighs 45kg, it does notneed a custom-built stand, and a solid table

will do. My MD65 progressed through twoother supports before settling on asecond-hand kitchen chopping table (1200x 500 x 900 WDH) that proved ideal for thetask. The lathe’s base casting has twomounting holes, but bolting to animperfectly true bench risks twisting thebed, so I covered the table top with carpettiles, sat the lathe on these and used themounting holes as locators for a pair ofbrass pillars drilled into the table top. Thecarpet tiles have the secondary benefit ofreducing noise, although I always wear earmuffs when using machine tools (photo 2).

WorkholdingThe head stock spindle has an MT2 taperto take a dead centre, and all other workholders are secured by three studs, eitherM5 or M6 onto an 80mm chuck flange(photo 3).

InstallationYou need access to the change wheelsand belts, so the headstock’s folded steelcover needs room to swing fully open, andyou need room at the right to operate theleadscrew’s control wheel. The manualstates 800 x 280mm, but these are lathedimensions, not the space needed, and1200 x 400mm is a realistic minimum. Thelathe will inevitably be pushed up againsta wall, and mine is in a dark corner, so Ihung a small book shelf above the lathe

and screwed a 2-foot fluorescent fitting tothe underside of its lowest shelf (photo 1).

I replaced the fitting’s choke ballast witha high frequency ballast to remove flicker,then added a shade to prevent direct sightof the tube. The original tube was replacedby an Osram L 18W965 from their Bioluxrange of tubes specifically designed forgood colour rendering and often used fortreating Seasonal Affective Disorder(SAD). They can be ordered from thedistributors that supply electricians andthe far superior light is well worth a littleextra expense.

This local uorescent light is excellent,but I wanted to be able to see what washappening when boring, so I drilled andtapped a pair of holes in the tail stock tofit a mains-powered LED spot lamp to thetail stock pointing roughly down thelathe’s axis. The spot lamp is connectedacross the lathe’s motor and its cable

Morgan Jones and hisHobbymat MD65

One ManLathe

andhis

1

2

Hobbymat MD65 under bookshelf having underslung fluorescent lamp.

General view of lathe on kitchen choppingtable, squeezed between boiler and fridge.



8/10/2019 mew225



Fitting the nuts and washers in the verylimited space behind the flange is fiddly,but the advantage over a screw-on chuckis that reversing the lathe does not riskmis-registration when screw cutting, orworse, a chuck unscrewing and droppingoff. I use an old pair of long-nosedelectrician’s pliers to locate and spin thenuts, then a spanner for final tightening.

The standard three-jaw chuck will getyou started, but I bought a four-jawindependent chuck as well, requiring acustom faceplate to match it to the chuck

flange. Custom face plates were readilyavailable when the lathe was new, butyou’d need to make your own now, sobear this in mind if offered a lathe withoutfour-jaw chuck (photo 4).

Millhill Supplies offered a 17.5 x R2 DIN6343 collet set and holder that covered3-13mm in 0.5mm steps, and given thelathe’s price, this was a substantialinvestment, but I needed to machine smallparts precisely from both ends. Theyoffered a cheaper version in 1mm steps,but not a separate set of the intermediate0.5mm collets for later upgrade, so Ibought the more complete set (photo 5).

Fitting the collet holder necessitatesmachining the lathe spindle to make itnearly an interference fit into the colletholder before securing with three M6socket screws. If offered a lathe with thiscollet set, check the fit of the collet holderon the spindle. Given that the collets are

house and lost the guard before usingthem. Similarly, a soft plastic sleeve slipsonto the head stock to shroud the rear ofthe chuck and must be removed each timethe chuck is changed. If the sleeve andchuck guard are still fitted, the lathe hasprobably not had much use!

TransmissionAs standard, the lathe’s 1 ⁄ 3 horse powersingle-phase 220VAC reversible motorhas a two-step pulley, a belt to thespring-tensioned four-step aluminiumintermediate pulley, and a second beltto the two-step phenolic tailstock pulley,giving speeds of 250, 500, 1000, and2000 rpm. Speed is easily changed bysimultaneously rotating and rolling a beltonto a smaller step, then rotating androlling the other end to the larger step. Ibought two spare belt sets when the lathewas new, but I’m still using the originals.

Screw cuttingEven 250 rpm is too fast for threadcutting. Essex Engineering supplied aspeed kit that added 78 and 156 rpm byreplacing the two-step motor pulley witha three-step version, and adding a secondintermediate pulley and third belt to therear of the machine. I don’t do a lot of

screw cutting, but the slow speed kit canbe useful for boring, so I’m glad I fitted it(photo 6).

The plastic change wheels might notinspire confidence, but twenty years’ lightuse suggests that they are fine providedthat they are kept oiled yet clean – themotor tends to blow fine swarf into thegear cavity. One change wheel (W) is onthe tail stock shaft and another (L) on thelead screw, with a pair of concentricintermediate wheels (Z1, Z2) on the banjo.Once the wheels are tted and meshed,drive to the lead screw is controlled by arather crude dog clutch.

The lathe has an M18 x 1 lead screw anda table on the head stock gives changewheels for particular thread pitches, butthe genius who created the table delightedin replacing multiple change wheels whena single replacement would do, andmissed some important threads. One day,

quite crude with only three slots and avery limited range of adjustment, acheaper/better solution might be ERcollets in a holder having an MT2 arborand draw bar (the internal bore of thespindle is 12mm).

Essex Engineering offered a 96mm Czechface plate, but I’ve only used it once as it isawkward to use. The problem is that the

face plate is only a little larger than thespinning flange, so the back of a work clampis obscured by the flange, making lifedifcult when securing and adjusting work.

Millhill Supplies supplied a centreturning kit and some rather poor fixedthree-point and travelling two-pointsteadies. (MEW issues 216 and 217 had agood two-part article by Alan Wain thatdescribed how to make a much betterfixed steady.)

GuardsAs originally supplied, the lathe had asmoked acrylic chuck guard hinged on along pin that screws into the head stock.The rst time you use an independent-jaw chuck you will shear the pin when thefurthest protruding jaw strikes it. I boughta set of screw extractors to remove theremains of the sheared pin, but moved

4

65

Custom face plate interfaces betweenflange and four-jaw chuck – note the M6nuts that secure the chuck in the smallgap between flange and head stock.

Space is limited in the transmissioncompartment – the slow speed attachmentcan just be seen at the bottom rear.

Collet chuck holder is secured by threeM6 socket screws.

3

80mm flange with MT2 internal taper and adjacent motor.



8/10/2019 mew225


›

53

One Man and his Lathe

February 2015

I needed a 0.9mm pitch thread, but thelathe claimed ignorance, so I spent sometime with a spreadsheet and devised amore complete version, table 1.

Note that in the new table, the nalchange wheel (L) stays at 100 wheneverpossible, partly because changing itrequires dog clutch disassembly, but alsobecause leaving it at 100 enables sensibleauto-feed cutting speeds.

Although British Association (BA)threads are specified in millimetres, and Ifound change wheel settings for them, fewperfectly match the 0.9n pitch requirement(n = BA number). The lathe can also cut farmore Imperial threads than claimed,mostly with <0.1% error.

The HardwareThe lathe’s saddle and tail stock run on a40mm ground steel D-bed supported at oneend by the tail stock’s aluminium castingand at the other by a substantial plate boltedto the base casting. My MD65 cuts a veryslight taper rather than perfect cylinders and

this minor (and seemingly uncorrectable)imperfection recently provoked a search forsomething bigger and better.

The saddle is permanently driven by thelead screw, with a control wheel at the farright of the lathe. The 1mm lead screw pitchallows the friction-locked dial to have majorgraduations of 0.1mm and minor of0.025mm. A lead screw conventionally pullsthe tool into the work, so the head stock endhas a thrust ball race to reduce friction, and Iadded one to the other end. Because thelead screw is a right hand thread engagingin the saddle, clockwise rotation drives thethread into the saddle, and since the threadis fixed but the saddle moveable, the saddlemoves towards the tail stock – the oppositeof most machines. Surprisingly,accustoming yourself to this reverseoperation doesn’t take long, even whengoing backwards and forwards betweenmachines, but it is a Hobbymat oddity.

The saddle has three screws on its back foradjusting play as it moves on the D-bed, butsome play or tightness is inevitable – thesolution is not quite as good as a dove tailslide plus gibs. The saddle draws a 280mmlong coaxial sleeve along the lead screw,significantly reducing (although noteliminating) its swarf exposure (photo 7).

The cross-slide is driven by an M6 x 1thread, so its control wheel dial has thesame graduations as the saddle, but

because the thread engages in the fixedsaddle and the thread moves, conventionalclockwise rotation drives the tool into thework.

The dovetail cross-slide has a gib adjustedby four lockable grub screws, and carefuladjustment allows smooth movement withnegligible play. The cross-slide can belocked in position, but this is done by a caphead screw bearing on the gib and possiblydistorting it, so I try not to use it (photo 8).

The top slide is one of the weak designpoints of the MD65, and is perhaps whythe cut-down MD200 incarnation omits it.

Table 1

Pitch(mm)

W Z1 Z2 L ISO coarse ISO fine BA

0.2 30 60 40 100

0.25 35 70 50 100

0.282 55 65 20 60 12

0.3 30 60 60 100

0.314 55 70 40 100 110.350 35 60 60 100 M1.6, M1.8 10

0.389 40 60 35 60 9

0.4 40 60 60 100 M2

0.431 35 65 40 50 8

0.45 60 40 30 100 M2.2, M2.5

0.477 35 55 75 100 7

0.5 50 60 60 100 M3

0.531 65 70 20 35 6

0.55 55 60 60 100

0.591 50 55 65 100 5

0.6 40 50 75 100 M3.5

0.65 65 60 60 1000.656 35 40 75 100 4

0.7 70 60 60 100 M4

0.729 35 60 50 40 3

0.75 75 60 60 100 M4.5

0.8 40 60 60 50 M5

0.808 35 40 60 65 2

0.9 60 40 60 100 1

1 60 30 50 100 M6 M8 0

1.1 55 60 60 50

1.2 60 75 60 40

1.25 50 60 60 40 M8 M10, M12

1.3 65 60 60 50

1.4 70 60 60 50

1.5 75 60 60 50 M10 M16, M20

1.6 40 50 70 35

1.75 70 60 60 40 M12

1.8 60 40 60 50

2 70 60 60 35 M14, M16 M24, M30

2.1 60 50 70 40

2.2 55 50 70 35

2.4 60 50 70 35

2.5 75 60 60 30 M18, M20,

M22

2.6 65 50 70 35

2.8 60 50 70 30

3 75 50 60 30 M24, M27 M36

87

RIGHT: The saddle is quite small. Note thetop slide gib adjustments and replacement

tool post. FAR RIGHT: With the top slideremoved, the cross slide jib adjustmentscan be seen to the right, as can the 4mm

pin that governs top slide rotation.



8/10/2019 mew225



10

11

The tail post with LED spot lamp and 6mm chuck – note thegraduated quill but ungraduated control wheel.

The reason theHobbymat wasbought – theauthor’s pick-uparm in action.

9

The top slide has been rotated to 45 degreesbut can be only secured by two screws…

The problem is that a 65mm swing doesn’treally leave enough room between the topof the tool tip to the lathe bed for all the

intervening parts. Thus the top slide isfastened directly to the cross slide by fourM5 screws, and its centre of rotation isdefined by a 4mm pin, with the fourscrews passing through a pair of cast arcs.Rotation is limited to about ±50 degrees,and even 45 degrees requires removingtwo screws, leaving only two screws tosecure the top slide (photo 9).

Like the cross slide, the top slide is drivenby an M6 x 1 thread, but the control wheelis smaller and has two handles, making itawkward to return quickly to the startingposition after a cut has been made. If thehandles were screwed in as all the othersare, removing one wouldn’t be a problem,but they’re pressed in, so removal withoutdamage would be difficult.

The dove tail top slide has gibadjustment and locking, but because itneeds to be thin, it is easily distorted bythe tool post, tightening movement atsome slide points. Unless perfectlyadjusted and lubricated, my top slide has atendency to cut slightly wavy lines.

Tool postThe standard tool post is so terrible that Ibinned it within a week of the new lathe’sarrival, so I can’t show you how awful it is.Suffice to say that it was a cylinder withan overhanging top lip having vertical

hex screws that tightened the tool directlyonto the top slide (thus distorting it).

Essex Engineering made an excellent4-way rotating tool post. Not only doesthe 4-way post allow adjustment of toolangle without compromising how tightlythe tool is held, but the tool post’s lowerflange reduces distortion of the top slide.The penalty of the rotating tool post is thatthe cutting tip must be <6mm from thebottom of the tool, tending to enforce6mm tools or smaller.

There isn’t enough room for a quick-change tool post, so you have to get usedto shimming tools to centre height, andthis is the final weak design point.

TailstockThe tailstock quill has an MT1 taper andthe supplied 10mm chuck had a keythat didn’t fit properly. I quickly bought

what the existence of the BFE65 millinghead implies, the MD65’s light cross slide onD-bed simply isn’t suited. I once used a slot

saw in the MD65 to cut the slots in analuminium collet I was making and keepingvibration to an acceptable level made thework very slow. A few months later I boughtthe proper tool for the job; a small mill.

When my eye is in, I can machine towithin a quarter thou (that’s <0.01mm forthe metric amongst you), and that wasgood enough to make the pick-up armwhich was finished in 1993 and has beenin use ever since (photo 11).

Friction in pick-up arms is crucial, so thearm is a unipivot (PTFE dimple resting onball point pen tip), which means thatbalancing on that single pointsimultaneously allows tilt and rotation(and twist, but we don’t talk about that).Although simple to make, unipivots arenotoriously difficult to align, so my chiefdesign aim was to make as manyadjustments independent of one anotheras possible, but that made some of thehidden machining quite tricky.

Electronics engineers are traditionallypoor at metalwork, and mine isn’texhibition quality, but I’m improving andit’s a rare week that doesn’t includemachining.

Overall impressionsThe Hobbymat MD65 is the ideal rst lathe.It is good enough to do quite serious work,

but not fashionable enough to be punitivelyexpensive. It is light enough to be usedupstairs and can be carried (at a pinch) byone person. It has taken me twenty years tooutgrow the MD65, so even though I nowhave a three-phase Colchester Bantam thatweighs almost ten times as much and is analtogether better machine, I’ll be keepingthe MD65 for small work. ■

a 12mm chuck with correctly fitting key,but ARCeurotrade.co.uk stock a very nice6mm chuck and JT1/MT1 arbor that is

much better for most work and thoroughlyrecommended (photo 10).

The cast iron tail stock is bored to slide onthe D-bed and locked/adjusted by twoscrews. Tightening the end screw opensthe slot, loosening the bore onto the bedand allowing freer movement, whereastightening the centre screw closes the slotto lock the tail stock in place. Correctadjustment of both screws is essential. Theend screw should be preset, and only thecentre screw used in operation – I leave along arm 6mm hex key in this screw.

Quill movement is achieved by an M8 x1.25 right hand thread, and because thethread is stationary but its nut movable,clockwise rotation pulls a drill away fromthe work – just like the lead screw. Thisreverse operation isn’t a problem, butbecause the thread is 1.25mm pitch, thecontrol wheel is ungraduated, althoughthe quill has 1mm graduations. When Ireally need to, I print a graduated papertape and stick it round the control wheel. Abetter solution would fit a yoke to the quillplus a digital gauge akin to those fitted topillar drills. Frankly, the problem occurs sorarely that an occasional printed stick-ongauge suffices for me.

Using the MachineThe MD65 is a little lathe. It isn’t big and it

isn’t heavy, so it flexes if you take a heavycut. Most of the time this is manageable,but two operations cause trouble. Partingis notorious for the tool digging in andprecipitating disaster; parting on the MD65is so nerve-wracking that I use a hacksaw.

Milling takes a discontinuous cut as eachcutting edge comes round and chips at thework. I don’t care what the manual says or



8/10/2019 mew225


NO SURCHARGE FOR DEBIT & CREDIT CARD PAYMENTS

BRITAIN’S FAVOURITE PHASE CONVERTERS... CE marked and EMC compliant

FREEPHONE 0800 035 2027 or 0121 708 4522

[email protected] • www.transwaveconverters.co.uk

REMOTE CONTROL STATION £67 inc VAT

2-YEAR WARRANTY/MONEY-BACK GUARANTEE

Suitable for all IMO inverters, this remote pendant allows you to

access the software of the inverter remotely, bypassing the

buttons on the inverter itself. START, STOP, FORWARD, REVERSE,

RUN, JOG, SPEED POTENTIOMETER. NO-VOLT RELEASE

safety feature and two metre

length of 7-core flex as standard.


240-volt 1-phase input, 240-volt 3-phase output (i.e. dual

voltage motor required). SOFT START-STOP, SPEED CONTROL,

BRAKING, MOTOR PROTECTION and JOG FUNCTIONS.

Low-Cost, general purpose simplified torque vector control.

Entry level performance suitable for the majority of

applications. Integral EMC Filter as standard. Four

sizes available from 0.4kW/0.5hp to 2.2kW/3hp.

,


240-volt 1-phase input, 240-volt 3-phase output (i.e. dual

voltage motor required). SOFT START-STOP, SPEED CONTROL,

BRAKING, MOTOR PROTECTION and JOG FUNCTIONS. Advanced vector control giving optimum

performance at low RPM. Four sizes from

0.4kW/0.5hp to 2.2kW/3hp.

JAGUAR VXR INVERTERS from £264 inc VAT

STATIC CONVERTERS from £264 inc VAT

240-volt 1-phase input, 415-volt 3-phase output.

Single or multi-motor operation via socket/plug or

distribution board. Eight sizes from 1.1kW/1.5hp

to 11kW/15hp.

Ideal solution for

“one machine at

a time” environments. Output retrofits directly to

existing machine wiring loom so no modification

to machine necessary. Manual power adjustment via switch using voltmeter as guide.


JAGUAR CUB INVERTERS from £174 inc VAT


240-volt 1-phase input, 240-volt 3-phase output

(i.e. dual voltage motor required). SOFT START-STOP, SPEED

CONTROL, BRAKING, MOTOR PROTECTION and JOG

FUNCTIONS. Simplified torque vector control

giving enhanced performance at low RPM.

Four sizes from 0.4kW/0.5hp to 2.2kW/3hp.


240-volt 1-phase input, 415-volt 3-phase output. Single or

multi-motor operation via socket/plug or distribution board.

Eleven sizes from 1.1kW/1.5hp to 22kW/30hp. Ideal

solution for multi-operator environments or where

fully automated “hands-free” operation is required

irrespective of demand. Output retrofits directly to existing machine wiring loom

so no modification to machine necessary. Some sizes suitable for welding applications.

ROTARY CONVERTERS from £504 inc VATR

CONVERTERS MADE IN BRITAIN SINCE 1984; 3-YEAR WARRANTY ON ALL

CONVERTER PRODUCTS; BS EN 9001:2008 QUALITY ASSURED MANUFACTURING

ENVIRONMENT; CE MARKED PRODUCTS COMPLIANT WITH EMC REGULATIONS,

THE LOW VOLTAGE DIRECTIVE and BS EN ISO 61000-3-2:2006.

.

i DRIVE INVERTERS from £119 inc VAT

THE

ONLY PHASE

CONVERTER MANUFACTURED IN

BRITAIN TO ISO9001:2008

by POWER CAPACITORS LTD

30 Redfern Road,Birmingham

B11 2BH

Inverter-Metric Motor-RCS packages from £228 inc VAT • Imperial Packages from £298 inc VAT

Ideal forMyford

& Boxfordlathes

Metric Motors from £60 including VAT Imperial Motors from £154 including VAT

SUP P ORT

BRIT ISH

MANUF ACT URI

NG

SUPPLYING

THE WOODWORKER

& MODEL ENGINEER

SINCE 1984

POWER CAPACITORS LTD

30 Redfern Road,Birmingham

B11 2BH



8/10/2019 mew225


3mm

36

34.08

2 off at least

4mm thick

1 at 4mm,

1 at 3mm

6mm

3/32

or 2.5mm 1 4 6


A written description or a part

to copy are not methods to berecommended. The latter can now

be done very accurately by a machinewhich scans the part with a laser and thenproduces a drawing. The former can onlybe used if an existing CAD file has to bechanged slightly. I have one particularcustomer who will say ‘Scale up part12036 by a factor of 1.43, then reduce theheight by 4mm’. This is fine for that partbut it is only possible because the originalwas to his design. Normally any form ofdescription is a non-starter.

Fag packet sketches are not usuallysufficient unless it is a very simple part andthe dimensions are all there. Better arepaper drawings but even then, as we are allaware, it is quite common for dimensionsto be missing. This is not too bad if it iscosmetic but when the main radius ismissing on an expansion link it can create afew scratched heads. I have often been

the only important dimension was the

overall height and this could be sorted outlater. After running the pdf file through theconverter the first thing to note was that theheight was wrong, it was too short. Thiswas due to scaling and easily corrected. TheCAD package I use will rescale by either afactor or to a reference length. So it was justa case of inputting the height required andthe computer did the rest. The top was notquite parallel with the base. This wascorrected by putting in a new line andjoining it up to the curves. The drawings areshown in fig. 1. Note that the software hasinterpreted the lower arc correctly but thetop one is over 100 short lines.

It is essential that the cutting line is onesingle continuous line, with no gaps andall on the same plane. The test is toconvert it into a polyline and it is at thisstage that many of the CAD files I receivefail. It has to be a single line. It isextremely easy when drawing something

asked if it is possible to scan in the

drawings. Well no, not really. The laser isaccurate to three thousandths of an inch; Idoubt the drawing is that accurate. Again ifit is a cosmetic piece it may be possible touse a scanner as we shall see later.

Normally I would redraw the part inCAD, inputting the dimensions in Imperialor Metric. The final drawing has to bedrawing exchange format (dxf) and on ametric template. Unfortunately if you usean imperial template your five inch gaugeSpringbok comes back from cutting in Ngauge! If anyone would like to make a B1in N gauge I can do them a deal on a setof frames.

Back to Neil, he sent me an Adobe Acrobatfile (pdf format) with the drawing on, whichI assume had been scanned in. There is afree package you can download called Aidepdf to dxf converter. I had used it oncebefore but not with any great success. Theparts Neil required cutting were not critical,

Producing CAD filesfor laser and water jet cuttingMalcom High offers some advice to readers lookingto have parts machine cut to their own designs.

Neil Wyatt asked me to

produce some laser cut

parts for a stand he had

to make for a stationary

engine. It raised the

question as to how

this could be done and

what form of drawing I

would require. Having

been producing parts

now for nearly a decade

I have been given this

information in many

different formats. Written

description, fag packet

sketch, pencil drawing and

CAD files just to mention a

few. It was decided a short

article on my experiences

might be useful.

Fig. 1

CAD drawing showing how

the software had interpreted

some arcs as lines



8/10/2019 mew225


57

Preparing Drawings for Laser Cutting

February 2015

fairly complex to get two lines on top ofeach other. The post processor whichconverts the dxf file into G code does notknow which line to follow, gets confusedand gives up in disgust. Some of the latestsoftware can overcome this, but it is bestto present the cutter with a perfect file.

Gaps are normally down to poor drawingpractice. All CAD packages will have snapcommands where the cursor will lock ontoanother line or curve. The chamfercommand can be set to zero and thenused to join two lines. The fillet commandis extremely useful in ensuring lines andcurves join. Another method is to use thetangent command rather than justsnapping onto the curve.

Normally when using a 2D package thelines will all be on the same plane. It doesnot have to be Z=0, any plane will do. With3D packages now becoming more popularthe problem of non-coplanar lines hasbecome more prevalent. What appears tohappen is that on exporting or saving thedrawing as a dxf the software cannotdecide whether to use the top of the plate

or the bottom of the plate as its line. Sosometimes it uses the top and sometimesthe bottom. What it means is the lines willnot join up. The first time I came acrossthis problem I could not understand whatwas happening. The cure is to change theproperties of the lines such that they areall on the same plane.

To get back to Neil’s stand, it wasnoticeable that on the CAD file the curveswere actually many short lines, theconversion software had not realised thelines were arcs. Zooming in on the linesrevealed that they had a saw toothappearance. This was to be expectedreally but since the height of the teeth wasonly a few microns it would not benoticeable on the final product whichwould need to be draw filed anyway.Worse were the two lines that doubledback on themselves - this would havecreated a shallow cut in the edge as seenin fig. 2. These were removed by deletingthe offending lines and drawing in newones. The only part that requiredredrawing was the base. This was no

the laser cutters. I often get asked if I dothe cutting myself. No, I subcontract that.Machines can cost one million pounds andneed a large building to house them.Nitrogen makers, gas tanks, stock roomand plenty of highly trained operatives arealso required, not something I would evenconsider. The expensive part is getting thefile ready for cutting. In the case of Neil’sstand that would be far more expensivethan the actual parts.

This was a fairly simple job comparedwith many I undertake. However it wasinteresting in that the conversion softwarewas very successful in producing the CADfile. The parts, photo 1, took the place of acasting which would have been far moreexpensive to have made, and yet the finalstand, photo 2, looks very convincing. ■

longer symmetrical and the lines did notjoin up. A simple part to do was the topwhich was the only part not on thedrawing. Finally the lines were all joinedup as a polyline.

To assist in the assembly operation theparts were tabbed and slotted. There is nohard and fast rule about this, if it looksright it probably is. The bases and top hadslots to accept the central plate and cutouts for the trim to go into. The tabs wereleft too long so they could be damaged onassembly if the parts were to be silversoldered. In this way they would not comeapart at 650 degrees centigrade. It wouldhave been possible to TIG weld the endsover if preferred.

With the files completed it was a case ofe-mailing them with a number of others to

1 2

The laser cut parts as supplied.

The standafter

fettling

andassembly

by Neil.

Fig. 2

The black line shows howthe conversion software had

interpreted the pdf file, it should

have followed the red line



8/10/2019 mew225



Competition and Loan Entries

The competition entries this year wereoutstanding (photo 1) – everyoneagreed it was possibly one of the bestever selections of entries. I won’t spoilthe write ups to be featured in ModelEngineer, I’ll just say it took the bestpart of an hour for all the prizes to bedistributed! Instead I’ll just mention someof the tooling in the loan and competitionclasses. Nor will I describe the huge hostof locos, boats, steam engines, trams andother products of busy workshops. Myapologies for failing to note down everyentrant’s name.

I was pleased to be able to bring alongMike Checkley’s machine vice (photo 2),which he was able to collect on theSunday. I have persuaded Mike to writeup the flexible stop, which he uses tofacilitate setting up for CNC machining.Carefully secured in a glass jar, Neil Readexhibited an ‘engineer’s emergency

Workshop Toolsat the Model Engineer Exhibition

MEW Editor, Neil Wyatt, journeyed down from the midlands to enjoyhis frst visit to the Model Engineer Exhibition at Sandown in December.

As I live well north of Brum, I was

delighted that the role of editor

gave me the excuse to spend

two days at the Model Engineer

Exhibition. I found almost as many

new things on my second day

as the first, and still didn’t get to

see as much of exhibits like theStirling Engine Society and the

full size traction engines as I had

wished. My focus was naturally on

workshop tooling and so I’d like to

pass on some of the flavour of the

exhibition to readers.

1907-2014

2

4

3

1

Mike Checkley’s device, as featuredin this issue.

An engineer’s emergency toolkit.

Giancarlo Mastrini’s Italian Prairie locomotive.

Collet tailstock.



8/10/2019 mew225


›

59

MEX 2014 Report

February 2015

toolkit’ (photo 3), which had as manyfunctions as a Swiss army knife,including some fine, if small, calipers.Other handy examples of workshoptooling included a collet tailstock (photo4) and a ‘keats’ angle plate from aHemingway kit (photo 5). One unusualand impressive display was a collectionof lost-wax patterns for a rotary engine,accompanied by a video of the engine inaction (photo 6).

6

5

7

Rotary engine patterns.‘Keats’ angle plate.

A spiral dividing head by Ivan Law.

8

Nick Farr restored this pillar drill.

10

9

11

Trident Mill modified by Ian Strickland.

Nick’s oil can to MogenKilde’s design.

This is Ian's R&B engine.

Chief Judge Ivan Law was obviouslyreticent about entering the competition,but he did bring along a fascinating spiraldividing head (photo 7), like an ordinaryone with another layer of complexity

added! Ivan expressed how keen he is to

see more tools entered into competition,stressing that tools should be well madewith a functional and appropriate finish– they don’t need to be silver plated orhave every visible surface hand-scraped to

win an award.Those who enjoy the reprints of old

plans from MEW at www.model-engineer.co.uk will recognise the name of Nick Farr,who took on the mammoth task ofscanning them all. Nick brought along hisimpressive restoration and update of anold sensitive drilling machine (photo 8),which I hope he will also write up for us,together with his interpretation of MogenKilde’s neat little oilcan (photo 9). Mogen’sdesign was published in a recent issue ofMEW , I’m sure I caught more than onevisitor using this beautifully polishedfabrication as a mirror!

From the tiny, to the huge. IanStrickland’s wonderful R&B engine iscurrently featured in MEW , to make it hehad to add a vertical milling head to hisTrident horizontal mill (photos 10 and 11).It’s now a very flexible and impressiveaddition to his workshop.



8/10/2019 mew225



Club StandsThe displays put on by the various modelengineering clubs were really diverse, and wealso had several operating (small gauge) railways,with three of them in live steam (photo 12).For the tool fan, a particular attraction was theSociety of Ornamental Turner’s display. Theyhad this wonderful rose engine by Birminghammanufacturer, Plants of Harborne (photo 13). Thediversity of cams (photo 14) was mind boggling,as were the many different slides and functions ofthe ornamental turning lathe that accompanied it

(photo 15).Other club stands focused mainly on models,

but there were several interesting tooling exhibitson display. The Ickenham club had a displayexplaining the intricacies of spiral milling,including several accessories (photo 16), whilstthe Surrey society display included a compacttapping tool (photo 17).

12

14

16

13

15

17

The East Surrey 16mm locomotive group.

The rose engine’s cams and micro-adjustment.

Spiral milling on the Ickenham stand.

Rose Engine on the SOT stand.

An ornamental turning lathe with tympan chuck.

A tapping toolfrom Surrey.



8/10/2019 mew225


To be continued...

61

MEX 2014 Report

February 2015

Trade StandsAlthough there were still plenty ofopportunities to empty your pockets, thetrade stands were missing a few familiarfaces this year. Nonetheless, Myfordexhibited both a new Connoisseur (photo18) and a beautifully refurbished ML7which featured newly tooled, and Britishmade, sensitive drilling and capstantailstock attachments (photo 19). Variablefrequency drive conversions are becomingincreasingly popular, and Transwave wereon hand offering much valuable advice(photo 20). Other trade stands offered awide range of small and large tool, fixingsand materials (from tiny short ends of brassto huge lumps of aluminium!) As well as therotary tables, cutters and chucks there weresome other unusual items (photo 21). Therewere some fine second hand machines, notleast a couple of shapers. I treated myselfto a little-used Osborn collet chuck at a verygood price. Another really nice little item Iwill leave un-named, though I’m sure manyreaders will instantly recognise it (photo 22).

18

20

22

19

21

The Myford stand.

Transwave and their range of motor solutions.

Can you guess what this is?

The refurbished ML7 with accessories.

A swarf rake?



8/10/2019 mew225


Scribe a line YOUR CHANCE TO TALK TO US!

Drop us a line and share your advice, questions and opinions with other readers.

Metal MindsDear Neil, I very much enjoyed readingMurray Eddington’s article ‘From Mind toMetal’ in MEW 221 and his explorationsand findings as regards CAD drawingprograms, 3D printing and machining.

In the article he mentioned that hedesigned and made a Spindle noseadaptor which allows D1-3 items/chucks to

be held on a rotary table. I have beenmulling over building one of these forages but haven't got round to it. I wonderif Murray would consider doing an articleon his design? There must be many otherswho also require such a device.

Peter Darveniza, Ballarat, Australia

Rust Removal (1)Dear Neil, Readers may be interested toknow that citric acid may be availablerelatively cheaply at a Home Brewingshop - £1.20 for 100 grams at my local onein Plymouth, and cheaper still in bulk. Itis used for correcting the acidity of a duffbatch of wine.

John Chapman

Rust Removal (2)Dear Neil, You ran an article on rustremoval by Robin Muir. Citric acid crystalsare easily available in ‘white sugar’ formfrom home brewing stores and online.I used it a lot as we live in a very hardwater area and it’s also good for descalingkettles. It seems to work on all metalsand especially on brass. I normally mixit in hot water adding crystals until the

solution is saturated and a few crystals lieundissolved on the bottom.

It works better if the solution is keptwarm. We have a central heating boiler inthe kitchen and an overnight soak isusually sufficient. One last thing - if you’rede-rusting steel don’t get it on your handsas the smell will linger for sometime!

Martin Akehurst, Henley-on-Thames

Choice of Motor?Dear Neil, I bought an Arrand Milling Spindle years ago intending to use it on mySuper 7 cross slide. A job which involves drilling screw holes in a face plate for awoodworking lathe has come up, but I’m at a loss on how to power the Spindle. Ihaven’t room in my workshop for an overhead pulley system and fixing an electricmotor to the cross slide seems the better option. The trouble is I can’t find a motorthat is small enough and able at the same time to provided sufficient power to drive

the Spindle. A 1/8 HP motor would probably suit but the ones on sale are too bulky.Can any reader suggest a solution?

Neil Macnaughtan, Edinburgh

Car Thermometer (1)Dear Neil, I got my latest copy of ModelEngineers Workshop no 223 on Saturdaylast, I was reading the scribe a line sectionre the vintage vehicle owned by Eric Paynof Jersey.

I think that the coloured fluid hedescribes is Alcohol, i.e. similar to the redstuff in a clinical thermometer. In the latel960s when I passed my driving test myfirst car was a 948 cc Triumph Heraldsaloon, and I wanted to tit a temperaturegauge to it. As it didn’t have any plug foran electrical one I fitted a similar devicewhich tapped into the top coolant hose.

It is vital on a car of this age that thecooling system is kept in tip top conditionas without a water pump it relies onthermo-syphon action where the hot waterrises to the top of the radiator and gets

cooled by the blast of air as the car travels,this was also common on pre and postwar ford cars.

There is a company advertising inPractical Classics that may be able to helpMr Payn. They are Speedy Cables(London) Ltd. Abercave Swansea SA9 1SQ.telephone 01639 732300.www. speedycables.com.

If he contacts them they may well beable to help him or if not they may knowof somebody who is capable of bothrepairing and re calibrating thisinstrument. I am of course putting in theusual disclaimer not having used this firmbut being a regular reader of this andother contemporary classic car magazines.

Hopefully this will be of some help to Eric.

J.E.Kirby, Stoke Newington


Eric Payn's Essex Super Six Pacemaker.

Robin'stest piece.



8/10/2019 mew225


63February 2014

Car Thermometer (2)Dear Neil, Regarding Eric Payn of Jersey‘squery about repairing a temperaturegauge, I had a similar task once but with adiaphragm instead of` a gauge. This is themethod that I used:

• Clean out the temperature bulb• Check that the capillary tube is clear• Anneal the capillary tube• Hard solder the sensor bulb

to the capillary tube.

The Red liquid being an unknown, couldI suggest either car brake fluid orautomatic gearbox oil? Fill a smallcontainer with fluid, and put the open endof the capillary tube under the fluidsurface. Then with the sensor bulb heldvertically, capillary tube at the top, gentlyheat the bulbuntil air bubbles stop comingout of the end of the capillary tube. Allowthe bulb to cool, this will draw liquid intothe bulb. Repeat the process until no moreair bubbles emerge.

received was issue 218. It seems that Ihave 6 issues missing!

I really do hope that these missing oneswill arrive.

All the very best for the festive seasonand keep up the good work.

Malcolm Cunnington,Johannesburg,South Africa

Now to the tricky bit, soft solder thecapillary tube to the gauge, Use soft solderas you may have to unsolder several timesto set the liquid level. The calibrationwould entail immersing the bulb in waterheated to the normal operatingtemperature of the car engine.

All the above is a tedious process butshould work.

Tony Stark, Newport, Gwent

Tired of WaitingDear Neil, I hope all is well in the UK andthat the winter is not treating you toobadly. Congratulations to all on the 25thanniversary.

I just wanted to tell you that we have hada 4 month long postal strike in SouthAfrica which was only resolved about 10days ago so there is a huge backlog ofmail, somewhere, and amongst thosepiles are my issue of MEW . The last one I

Scribe a Line

We would love to hear your comments, questions and feedback about MEWWrite to The Editor, Neil Wyatt, Model Engineersʼ Workshop, MyTimeMedia Ltd., Enterprise House, Enterprise Way,

Edenbridge, Kent TN8 6HF. Alternatively, email: [email protected]

Relay QueryDear Sir, I am going to install a‘Power Axis Motion’ as described byDavid Reece in issue 214 of ModelEngineers Workshop .

Would somebody please advise meas to what relays were used or to use.

H Cormick

This book is not what I expected it tobe, and I must admit I thought twicebefore including a short review here.

The scale models in the book are a tree,a chair, a room and a human figure – and

somewhat incongruously – a colourfulexploding star, which, along with a plaincube, is an exercise in technique ratherthan anything else. The audience for thisbook are raw beginners, and the subjectis scene setting – from ‘doll’s houses andor [a] model railway landscape’ to ‘a smallpiece of sculpture’. The raw materials arelargely card and other ‘craft’ media, suchas clay. It’s not a book about engineering.

Mark friend’s approach to models is nota precise ‘rivet counter’ one, it is not eventhat of the architectural modeller. Rather,his models are impressionistic, conveyingatmosphere rather than claiming to beexact replicas. He is up front that this bookis about where craft and art merge.

And that’s why I’m writing this shortreview. I’m struck by his simple model of asuited male figure. Accuratelyproportioned, but lacking detail, it stillmanages to convey a sense of action and

even apprehension. Many engineeringmodels would benefit hugely from a‘diorama’ type setting, and while it ispossible to create accurate models ofworkshops and engine houses, the figureswe see with even the finest models rarelyhave more than the appearance of dolls,just standing as decorations rather thanreally being part of the scene.

My thought is that figures, and otherelements of the setting of modelsproduced along the lines described in thisbook, could well be an effective way ofpresenting some engineering models.Appearing engaged with the subject of thediorama, but not competing with it interms of detail they could bring real lifeinto the scene.

Book ReviewMaking Scale Modelsby Mark Friend

ISBN 978 1 84797 770 0Published by The Crowood Press

£ 9. 9 9



8/10/2019 mew225


Toadvertiseonthesepages

contactDuncanArmstron

gon08448485238ordu

ncan.armstrong@mytimem

edia.com

All advertisements will be inserted in the first available issue.There are no reimbursement for cancellations. All advertisement must be pre-paid.The Business Advertisements (Disclosure) Order 1977 - Requires all advertisementsby people who sell goods in the course of business to make that fact clear.Consequently all trade ads in Model Engineers’ Workshop carry this ‘T’ symbol

64 www.model-engineer.co.uk Model Engineers’ Workshop February 2015

emplate indd 1 09/05/2014 16:06



8/10/2019 mew225


All advertisements will be inserted in the first available issue.There are no reimbursement for cancellations. All advertisement must be pre-paid.The Business Advertisements (Disclosure) Order 1977 - Requires all advertisementsby people who sell goods in the course of business to make that fact clear.Consequently all trade ads in Model Engineers’ Workshop carry this ‘T’ symbol

T o a d v e r t i s e o n t h e s e p a g e s

c o n t a c t D u n c a n A r m s t r o n

g o n 0 8 4 4 8 4 8 5 2 3 8 o r d u

n c a n . a r m s t r o n g @ m y t i m e m

e d i a . c o m

65Model Engineers’ Workshop February 2015



8/10/2019 mew225


Remap is a charity

that helps children

and adults with

disabilities to achieve

greater independence

and enjoyment of

life’s opportunities.

Our volunteers make

special one-off pieces

of equipment and

everything we do

is given free to our

clients.

Join usand use your skills to helpchildren and

adults

Find out more atwww.remap.org.uk

email:volunteer

@remap.org.uk

or telephone0845 1300 456

Registered Charity Number 113766



8/10/2019 mew225


Weiler lathe + collets

1Acision lathe + collets

144 Maidstone Road, Foots Cray, Sidcup, Kent DA14 5HS Telephone: 0208 300 9070 - Evenings: 01959 532199 - Facsimile: 0208 309 6311

www.homeandworkshop.co.uk • [email protected] Opening Times: Monday-Friday 9am-5.30pm - Saturday Morning 9am-1pm 10 minutes from M25 - Junction 3 and South Circular - A205

Emirbeechbench£1650

>

Harrisonvertical mill

Scheppach Basato 4 sawMeddings

M10 precision drill + inverter

£1450

MyfordSuper 7B

£1225Myford ML7

£3450

Myford Super 7B

3½” x 31”rare long bed £2750

£1750

MYFORD Super 7BBeautifulBeautiful!

£3950

Myford ML7R

£2350

Myford ML7 /Super 7 Rifle /Bridge bed felts

Bridgeportlotting head

25

ReductionReduction NOW onlyNOW only

£245 to Clear£245 to Clear

TaylorHobson Kengraver

TomSeniorM1 mill

£495

Startrite 275saw + brakeslidingtableewnew

Myford ML7B + stand

HOME AND WORKSHOP MACHINERY

750Boxford 1130 lathe

Hobbymat lathe £425

ust a small selection of our current stock photographed!

e are currently seeking late ` Myford Super 7B´ & `Super 7 large bore´ model lathes!

£20ach

D-40

£3450>

Startrite18-S-5bandsaw

£950 >

£2250

VeryVery

nicenice!

>

StartriteEF1 3MTgeared

dill

£1150

VariousVarious Angle plates + surface plates

>

£625 >

Myford9" faceplate

£60

£495 >

£950

Startrite352 wood/ brass/aluminium,two speed 240 volts

Sylvac1 metre vernier boxed!

£5 each

Bright mild & leadbearing steel x 24”

£575

£3450

Colchester Bantam2000 lathe

MeddingsMF5 bench drill

£245

Viceroy buffer

Special 5 for £20

>

Flamefast DS320brazing hearth/forge

£425 >

MYFORD GENUINE PARTS Running out fast!!

Purchased from Nottingham check the web site for full list!

SHIPPINGWORLDWIDE

New even easier to use Web siteNew even easier to use Web site!

>

LEASE PHONE 0208 300 9070 TO CHECK AVAILABILITY OR TO OBTAIN OUR LIST

ISTANCE NO PROBLEM! • DEFINITELY WORTH A VISIT • ALL PRICES EXCLUSIVE OF VAT

£3450

ToolingToolingfor salefor sale!

£1750Edwards

.25M / 5ft x 16g + guards

£575Lorch lathe+ collets 240volts

Elliot

JuniorOmnimill+ inverter 28" x 7"

£3250

Tripus (German) on/off switch

£90 >

>

£1425Myford ML7

£170newnew!

Precision Stanier55mm machine vice from New Zealand

Models• 31/2" RobRoy chassis,castings, plans etc. £475• 5" Pansey chassis,

castings, plans etc. £750

GabroBF620 24"box folder

£375

Berco mowergrindingmachine

£2450

Myford Super 7

£2450

>

New To clearNew 'To clear' section on websitesection on website

£3450

Just inJust in!

£375 Tom Senior dividinghead + two plates£725

>

Fodengenuine Ballasttractor (Full Size)

£14950(No VAT)

New photosNew photoson web siteon web site

Myford Super 7B Plus bigbore, Tesla ML750 + NewallDRO, long hardened bed

£6950

>

Boxford AUD lathe

£1400

Emco FB11 mill+ powered table & DRO

£2750

Fobco 7EIGHT 7/8"back geared ped. drill

£625

>

>Harrison M300 lathe









8/10/2019 mew225


Documents

mew225