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7/29/2019 Workshop manual for fitting,welding and machine shop
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Indian Institute of Technology Hyderabad
ME 101: WORKSHOP PRACTICE I
Pushing frontiers
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April 2009PREFACE
Theengineerscancreateanewkindofcivilization,basedontechnology,whereart,beautyand
finerthingsoflifeareacceptedaseveryonesdue.Engineers,whateverbetheirlineofactivity,mustbe
proficientwithallaspectsofmanufacturing.However, itshouldnotbeforgottenthatpracticewithout
theory isblindand the theorywithoutpractice is lame.Aperson involved inacquiringmanufacturing
skillsmusthavebalancedknowledgeoftheoryaswellaspractice.Thisbook iswrittentomeet theobjectivesof thetrainingcourses inworkshoppracticeforall
the first year engineering courses in Indian institute of technology Hyderabad. It imparts basic
knowledgeofvarioustoolsandtheiruseindifferentsectionsofmanufacturesuchasfitting,carpentry,
welding,machineshopetc.
Thestudyofworkshoppracticeactsas thebasis for further technicalstudies.Thisbookgives
theperceptiontobuildtechnicalknowledgebyactingasaguideforimpartingfundamentalknowledge.
Numerousneatlydrawn illustrationsprovided in the textwillhelp the students inunderstanding the
subject,andtheconceptsrelatedit,better.
Sincereattemptshavebeenmadetopresentthecontentsinasimplelanguage,supplemented
withlinediagrams,whichareselfexplanatoryandeasytoreproduce.
Wewould like toexpressoursincere thanks toprofessorsandcolleagues for theirconsistent
support.Suggestionsforimprovementinthisbookwillbethankfullyacknowledgedandincorporatedinthenextedition.
K.SathyanarayanaN.A.Somasundaram
P.Raju
25April2009
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Contents
PrefaceTableofContents page1.FittingShop
1.1
Introduction
1.2 Holdingtools
1.3 Markingandmeasuringtools
1.4 Cuttingtools
1.5 Finishingtools
1.6 Miscellaneoustools
1.7 Safepractice
1.8 Modelsforpreparation
Exercises
1
1
2
5
8
10
11
12
13
2.Carpentry
2.1 Introduction
2.2 Timber
2.3
Markingand
measuring
tools
2.4 Holdingtools
2.5 Planingtools
2.6 Cuttingtools
2.7 Drillingandboringtools
2.8 Miscellaneoustools
2.9 Woodjoints
2.10 Safe practice
Exercises
15
15
16
17
18
28
20
21
22
24
25
3.Welding
3.1 Introduction
3.2 Arcwelding
3.3 Weldingtools
3.4 Techniquesofwelding
3.5 Typesofjoints
3.6 Weldingpositions
3.7 Advantages&disadvantagesofarcwelding
3.8 Safepractice
Exercises
28
28
30
31
32
33
33
34
35
4.MachineShop
4.1 Introduction
4.2 Lathe
4.3 Workholdingdevices
4.4 Measuringtools
4.5 Cuttingparameters
4.6 Toolmaterials
4.7 Toolgeometry
4.8 Latheoperations
4.9 Safetyprecautions
39
39
40
40
41
41
42
42
44
Exercises 45
References 48
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Chapter1
FITTINGSHOP
1.1INTRODUCTION
Machine toolsare capableofproducingworkata faster rate,but, thereareoccasionswhen
components are processed at the bench. Sometimes, it becomes necessary to replace or repair
componentwhichmustbefitaccuratelywithanothercomponentonreassembly.Thisinvolvesacertainamountofhand fitting.The assemblyofmachine tools,jigs,gauges,etc, involves certainamountof
benchwork.Theaccuracyofworkdonedependsupontheexperienceandskillofthefitter.
Thetermbenchworkreferstotheproductionofcomponentsbyhandonthebench,whereas
fittingdealswhichtheassemblyofmatingparts,throughremovalofmetal,toobtaintherequiredfit.
Both the bench work and fitting requires the use of number of simple hand tools and
considerablemanual efforts. The operations in the aboveworks consist of filing, chipping, scraping,
sawingdrilling,andtapping.
1.2HOLDINGTOOLS
1.2.1Benchvice
Thebenchviceisaworkholdingdevice.Itisthemostcommonlyusedviceinafittingshop.The
benchviceisshowninFigure1.1.
Figure1.1:BenchVice
Itisfixedtothebenchwithboltsandnuts.Thevicebodyconsistsoftwomainparts,fixedjaw
andmovablejaw.When thevicehandle is turned inaclockwisedirection, the slidingjaw forces the
workagainstthefixedjaw.Jawplatesaremadeofhardenedsteel.Serrationsonthejawsensureagood
grip.Jawcapsmadeofsoftmaterialareusedtoprotectfinishedsurfaces,grippedinthevice.Thesizeof
theviceisspecifiedbythelengthofthejaws.
The vice body ismade of cast Ironwhich is strong in compression,weak in tension and so
fracturesundershocksandthereforeshouldneverbehammered.
1.2.2Vblock
Vblock isrectangularorsquareblockwithaVgrooveononeorbothsidesopposite toeach
other.TheangleoftheVisusually900.Vblockwithaclampisusedtoholdcylindricalworksecurely,
during layout of measurement, for measuring operations or for drilling for this the bar is faced
longitudinally in theVGrooveand thescrewofVclamp is tightened.Thisgrip therod is firmwith its
axisparalleltotheaxisofthevgroove.
1.2.3CClamp
Thisisusedtoholdworkagainstanangleplateorvblockoranyothersurface,whengrippingis
required.
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ItsfixedjawisshapedlikeEnglishalphabetCandthemovablejawisroundinshapeanddirectly
fittedtothethreadedscrewattheend.Theworkingprincipleofthisclamp isthesameasthatofthe
benchvice.
Figure1.2:Vblock Figure1.3:Cclamp
1.3
MARKING
AND
MEASURING
TOOLS
1.3.1Surfaceplate
The surfaceplate ismachined to fine limitsand isused for testing the flatnessof thework
piece.Itisalsousedformarkingoutsmallboxandismorepreciousthanthemarkingtable.Thedegree
ofthefinisheddependsuponwhetherit isdesignedforbenchwork inafittingshoporforusing inan
inspectionroom;thesurfaceplateismadeofCastIron,hardenedSteelorGranitestone.Itisspecified
bylength,width,heightandgrade.Handlesareprovidedontwooppositesides,tocarryitwhileshifting
fromoneplacetoanother.
Figure1.4:Surfaceplate Figure1.5:Angleplate
1.3.2Trysquare
Itismeasuringandmarkingtoolfor900angle.Inpractice,itisusedforcheckingthesquarenessofmany typesofsmallworkswhenextremeaccuracy isnot required .Thebladeof theTry square is
madeofhardenedsteelandthestockofcastIronorsteel.ThesizeoftheTrysquareisspecifiedbythe
lengthoftheblade.
1.3.3Scriber
AScriberisaslendersteeltool,usedtoscribeormarklinesonmetalworkpieces.Itismadeof
hardenedandtemperedHighCarbonSteel.TheTipofthescriberisgenerallygroundat12oto15o.
Itisgenerallyavailableinlengths,rangingfrom125mmto250mm.Ithastwopointedendsthebentend
isusedformarkinglineswherethestraightendcannotreach.
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Figure1.6:Trysquare Figure1.7:Scriber
1.3.4OddlegCaliper
ThisisalsocalledJennyCaliperorHermaphrodite.Thisisusedformarkingparallellinersfrom
afinishededgeandalsoforlocatingthecenterofroundbars; ithasone legpointed likeadividerand
theother
leg
bent
like
acaliper.
Itisspecified
by
the
length
of
the
leg
up
to
the
hinge
point.
1.3.5Divider
It isbasically similar to the calipersexcept that its legs are kept straight andpointed at the
measuringedge.Thisisusedformarkingcircles,arcslayingoutperpendicularlines,bysettinglines.Itis
madeofcasehardenedmildsteelorhardenedand tempered lowcarbonsteel. Itssize isspecifiedby
thelengthoftheleg.
Figure1.8:Oddlegcaliperanddivider
1.3.6Trammel
Trammelisusedfordrawinglargecirclesorarcs.
1.3.7Punches
Theseareusedformakingindentationsonthescribedlines,tomakethemvisibleclearly.Thesearemadeofhighcarbonsteel.Apunchisspecifiedbyitslengthanddiameter(sayas15012.5mm).It
consistsofacylindricalknurledbody,whichisplainforsomelengthatthetopofit.Attheotherend,it
isgroundtoapoint.Thetaperedpointofthepunchishardenedoveralengthof20to30mm.
Dotpunch is used to lightly indent along the layout lines, to locate center of holes and toprovidea smallcentermark fordividerpoint,etc. for thispurpose, thepunch isground toaconical
pointhaving60includedangle.
Centerpunch issimilartothedotpunch,exceptthat it isgroundtoaconicalpointhaving90includedangle.Itisusedtomarkthelocationoftheholestobedrilled.
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Figure1.9:Punches
1.3.8Calipers
Theyareindirectmeasuringtoolsusedtomeasureortransferlineardimensions.Theseareused
with the help of a steel Rule to check inside and outsidemeasurements. These aremade of Case
hardenedmildsteelorhardenedandtemperedlowcarbonsteel.Whileusing,butthelegsofthecaliper
aresetagainstthesurfaceofthework,whetherinsideoroutsideandthedistancebetweenthelegsis
measuredwiththehelpofascaleandthesamecanbetransferredtoanotherdesiredplace.Theseare
specifiedbythelengthoftheleg.Inthecaseofoutsidecaliper,thelegsarebentinwardsandinthecase
ofinsidecaliper,thelegsbentoutwards.
Figure1.10:Calipers
1.3.9VernierCalipers
Theseareused formeasuringoutsideaswellas insidedimensionsaccurately. Itmayalsobe
usedasadepthgauge.Ithastwojaws.Onejawisformedatoneendofitsmainscaleandtheotherjaw
ismadepartofavernierscale.
Figure1.11:Verniercaliper
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1.3.10VernierHeightGauge
TheVernierHeightgaugeclampedwithascriber.ItisusedforLayoutworkandoffsetscriberis
usedwhen it isrequired to takemeasurement from thesurface,onwhich thegauge isstanding.The
accuracyandworkingprincipleof thisgaugeare the sameas thoseof theverniercalipers. Its size is
specifiedbythemaximumheightthatcanbemeasuredbyit.ItismadeofNickelChromiumSteel.
Figure1.12:VernierHeightgauge
1.4CUTTINGTOOLS
1.4.1HackSaw
TheHackSawisusedforcuttingmetalbyhand.Itconsistsofaframe,whichholdsathinblade,
firmly inposition.Hacksawblade isspecifiedby thenumberof teeth forcentimeter.Hacksawblades
haveanumberofteethrangingfrom5to15percentimeter(cm).Bladeshavinglessernumberofteeth
percmareusedforcuttingsoftmaterialslikealuminum,brassandbronze.Bladeshavinglargernumber
ofteethpercentimeterareusedforcuttinghardmaterialslikesteelandcastIron.
Hacksawbladesareclassifiedas(i)Allhardand(ii)flexibletype.Theallhardbladesaremadeof
H.S.S,hardenedand tempered throughout to retain theircuttingedges longer.Theseareused tocut
hardmetals.Thesebladesarehardandbrittleandcanbreakeasilybytwistingandforcingthemintothe
workwhilesawing.FlexiblebladesaremadeofH.S.Sorlowalloysteelbutonlytheteetharehardened
and the restof theblade is softand flexible. Theseare suitable forusebyunskilledor semiskilled
persons.
Figure1.13:Hacksawframewithblade
Theteethofthehacksawbladearestaggered,asshowninfigureandknownasasetofteeth.
Thesemakeslotswiderthanthebladethickness,preventingthebladefromjamming.
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Figure1.14:Setofteeth
1.4.2Chisels
Chiselsareused for removing surplusmetalor for cutting thin sheets.These toolsaremade
from0.9%to1.0%carbonsteelofoctagonalorhexagonalsection.Chiselsareannealed,hardenedand
temperedtoproduceatoughshankandhardcuttingedge.Annealingrelievestheinternalstressesina
metal.Thecuttingangleofthechiselforgeneralpurposeisabout60.
Figure1.15:Flatchisel
1.4.3TwistDrill
Twistdrillsareused formakingholes.ThesearemadeofHighspeed steel.Bothstraightand
tapershanktwistdrillsareused.Theparallelshanktwistdrillcanbeheldinanordinaryselfcentering
drillcheck.The tappershank twistdrill fits intoacorresponding taperedboreprovided in thedrilling
machinespindle.
Figure1.16:Twistdrills
1.4.4TapsandTapwrenches
Atapisahardenedandsteeltool,usedforcuttinginternalthreadinadrillhole.HandTapsare
usually supplied in setsof three ineachdiameterand thread size.Each setconsistsofa tapper tap,
intermediatetapandplugorbottomingtap.Tapsaremadeofhighcarbonsteelorhighspeedsteel.
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Figure1.17:Tapsandtapwrench
1.4.5Diesanddieholders
Diesare thecutting toolsused formakingexternal thread.Diesaremadeeithersolidorsplit
type.Theyarefixedinadiestockforholdingandadjustingthediegap.TheyaremadeofSteelorHigh
CarbonSteel.
Figure1.18:Diesanddieholder
1.4.6
Bench
Drilling
Machine
Holesaredrilled for fasteningpartswithrivets,boltsor forproducing internal thread.Bench
drillingmachineisthemostversatilemachineusedinafittingshopforthepurpose.Twistdrills,madeof
toolsteelorhighspeedsteelareusedwiththedrillingmachinefordrillingholes.
Followingarethestagesindrillingwork
1. Selectthecorrectsizedrills,putitintothecheckandlockitfirmly
2. Adjustthespeedofthemachinetosuittheworkbychangingthebeltonthepulleys.Usehighspeed
forsmalldrillsandsoftmaterialsandlowspeedforlargediameterdrillsandhardmaterials.
3. Layoutofthelocationofthepoleandmarkitwithacenterpunch.
4. Holdtheworkfirmlyintheviceonthemachinetableandclampitdirectlyontothemachinetable.
5. Putonthepower,locatethepunchmarkandapplyslightpressurewiththeFeedHandle.
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6. OnceDrilling is commencedat the correct location,applyenoughpressureand continuedrilling.
Whendrillingsteelapplycuttingoilatthedrillingpoint.
7. Release the pressure slightly,when the drill point pierces the lower surface of themetal. This
preventsthedrillcatchinganddamagingtheworkordrill.
8. Oncompletionofdrillingretracethedrilloutoftheworkandputoffthepowersupply.
Figure1.19:Benchdrill
1.5FINISHINGTOOLS
1.5.1Reamers
Reaming isanoperationof sizingand finishingadrilledhole,with thehelpofa cutting tool
called reamerhaving a number of cutting edges. For this, a hole is first drilled, the sizeofwhich is
slightlysmaller
than
the
finished
size
and
then
ahand
reamer
or
machine
reamer
isused
for
finishing
theholetothecorrectsize.
HandReamerismadeofHighCarbonSteelandhaslefthandspiralflutessothat,itisprevented
fromscrewingintothewholeduringoperation.TheShankendofthereamerismadestraightsothatit
canbeheldinatapwrench.Itisoperatedbyhand,withatapwrenchfittedonthesquareendofthe
reamerandwiththeworkpieceheld inthevice.Thebodyofthereamer isgivenaslighttapperat its
workingend,foritseasyentryintothewholeduringoperation,itisrotatedonlyinclockwisedirection
andalsowhileremovingitfromthewhole.
Figure1.20:Reamers
1.5.2Files
Filingisoneofthemethodsofremovingsmallamountsofmaterialfromthesurfaceofametal
part.Afileishardenedsteeltoo,havingsmallparallelrowsofcuttingedgesorteethonitssurfaces.
Onthefaces,theteethareusuallydiagonaltotheedge.Oneendofthefileisshapedtofitinto
awoodenhandle.The figureshowsvariouspartsofahand file.Thehand file isparallel inwidthand
taperingslightly inthickness,towardsthetip.It isprovidedwithdoublecutteeth.Onthefaces,single
cutononeedgeandnoteethontheotheredge,whichisknownasasafeedge.
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Figure1.21:Partsofahandfile
Filesareclassifiedaccording totheirshape,cutting teethandpitchorgradeofthe teeth.The
figureshowsthevarioustypesoffilesbasedontheirshape.
Figure1.22:Singleanddoublecutfiles
Needlefile
Figure1.23:Typesoffiles
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1.6MISCELLANEOUSTOOLS
1.6.1Filecard
Itisametalbrush,usedforcleaningthefiles,tofreethemfromfilings,cloggedinbetweenthe
teeth.
Figure1.24:Filecard
1.6.2Spiritlevel
Itisusedtocheckthelevelingofmachines.
1.6.3Ball PeenHammer
Ball PeenHammersarenamed,dependingupontheirshapeandmaterialandspecifiedbytheir
weight.Aballpeenhammerhasaflatfacewhich isusedforgeneralworkandaballend,particularly
usedforriveting.
Figure1.25:Ballpeenhammer
1.6.4CrossPeenHammer
It is similar to ball peen hammer, except the shape of the peen. This is used for chipping,
riveting,bendingandstretchingmetalsandhammeringinsidethecurvesandshoulders.
1.6.5StraightPeenHammer
Thisissimilartocrosspeenhammer,but itspeen is inlinewiththehammerhandle.Itisused
forswaging,rivetinginrestrictedplacesandstretchingmetals.
Figure1.26:Crosspeenhammer Figure1.27:Straightpeenhammer
1.6.6Screwdriver
Ascrewdriverisdesignedtoturnscrews.Thebladeismadeofsteelandisavailableindifferent
lengthsanddiameters.Thegrindingofthetiptothecorrectshapeisveryimportant.
Astarscrewdriverisspeciallydesignedtofittheheadofstarscrews.Theendofthebladeisfluted
insteadofflattened.Thescrewdriverisspecifiedbythelengthofthemetalpartfromhandletothetip.
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Figure1.28:Screwdrivers
1.6.7Spanners
Aspannerorwrenchisatoolforturningnutsandbolts.Itisusuallymadeofforgedsteel.There
aremanykindsofspanners.Theyarenamedaccordingtotheapplication.Thesizeofthespanner
denotesthesizeoftheboltonwhichitcanwork.
Figure1.28:Spanners
1.7SAFEPRACTICE
Thefollowingaresomeofthesafeandcorrectworkpracticesinbenchworkandfittingshop,with
respecttothetoolsused
1.Keephandsandtoolswipedcleanandfreeofdirt,oilandgrease.Drytoolsaresafertousethan
slipperytools.
2.Donotcarrysharptoolsonpockets.
3.Wearleathershoesandnotsandals.
4.Dontwearlooseclothes.
5.Donokeepworkingtoolsattheedgeofthetable.
6.Positiontheworkpiecesuchthatthecuttobemadeisclosetothevice.Thispracticeprevents
springing,sawbreakageandpersonalinjury.
7.Applyforceonlyontheforward(cutting)strokeandrelievetheforceonthereturnstrokewhile
sawingandfiling.
8.Donotholdtheworkpieceinhandwhilecutting.
9.Usethefilewithaproperlyfittedtighthandle.
10.Afterfiling,removetheburrsfromtheedgesofthework,topreventcutstothefingers.
11.Donotuseviceasananvil.
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12.Whilesawing,keepthebladestraight;otherwiseitwillbreak
13.Donotuseafilewithouthandle.
14.Cleantheviceafteruse.
1.8MODELSFORPRACTICE
Preparethemodels,asperthedimensionsandfitsshowninbelow.
Figure1.30:DovetailFitting Figure1.31:Vfitting
Figure1.32:Halfroundfitting Figure1.33:Crossfitting
Figure1.34:DrillingandTapping
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ME101WorkshopPracticeI Fitting
Exercise1SquareFiling
Aim
TofilethegiventwoMildSteelpiecesintoasquareshapeof48mmsideasshowninFigureFE1Toolsrequired
Benchvice,setofFiles,Steelrule,Trysquare,Verniercaliper,Vernierheightgauge,Ballpeenhammer,
Scriber,Dotpunch,Surfaceplate,AngleplateandAnvil.
Sequenceofoperations
1. Thedimensionsofthegivenpiecearecheckedwiththesteelrule.
2. Thejob isfixedrigidly inabenchviceandthetwoadjacentsidesarefiled,usingtheroughflatfile
firstandthenthesmoothflatfilesuchthat,thetwosidesareatrightangle.
3. Therightangleofthetwoadjacentsidesischeckedwiththetrysquare.
4. Chalkisthenappliedonthesurfaceoftheworkpiece.
5. Thegivendimensionsaremarkedbyscribingtwolines,withreferencetotheabovetwodatumsides
byusingVernierheightgauge,AngleplateandSurfaceplate.
6. Usingthe
dot
punch,
dots
are
punched
along
the
above
scribed
lines.
7. Thetwosidesarethenfiled,byfittingthejobinthebenchvice;followedbycheckingtheflatnessof
thesurfaces.
Asthematerialremovalthroughfilingisrelativelyless,filingisdoneinsteadofsawing.ResultThesquarepiecesof48mmsideisthusobtainedbyfiling,asdiscussedabove.
a.Rawmaterial b.Finishedjob
FigureF E1:Squarefiling
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ME101WorkshopPracticeI Fitting
Exercise2VFitting
Aim
TomakeV fitfromthegiventwoMSplates anddrillingandTappingas showninFigureFE2Toolsrequired
Benchvice,setofFiles,Trysquare,Scriber,Steelrule,Ballpeenhammer,Dotpunch,Hacksaw, Vernier
caliper,Surfaceplate,Angleplate,Vernierheightgauge,5mmdrillbit,3mmdrillbit,M6 tapsetwith
wrench,AnvilandDrillingmachine.
Sequenceofoperations
1. Theburrsinthepiecesareremovedandthedimensionsarecheckedwithsteelrule.
2. MakebothpiecessurfacelevelsandrightanglesbyfixingintheVice,useFilesforremovingmaterial
togetlevel.
3. WiththehelpofTrysquarechecktherightanglesandsurfacelevels.
4. UsingSurfaceplateandAngleplatemark thegiven twometalpiecesasperdrawingwithVernier
heightgauge.
5. Punch
the
scribed
lines
with
dot
punch
and
hammer
keeping
on
the
Anvil.
Punch
to
punch
give
5
mmgap.
6. CutexcessmaterialwherevernecessarywithHacksawframewithblade,DrillbitsandTaps.
7. The corners and flat surfaces are filed by using square/flat and triangular file to get the sharp
corners.
8. Dimensions are checked by vernier caliper and match the two pieces. Any defect noticed, are
rectifiedbyfilingwithasmoothfile.
9. Care is taken tosee that thepuncheddotsarenotcrossed,which is indicatedby thehalfof the
punchdotsleftonthepieces.
ResultTherequiredV fittingisthusobtained,byfollowingthestages,asdescribedabove.
FigureF E2:VFitting
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Chapter2
CARPENTRY
2.1INTRODUCTION
Carpentrymay be defined as the process ofmaking wooden components. It starts from a
marketableformofwoodandendswithfinishedproducts. It6dealswiththebuildingwork,furniture,
cabinetmaking.Etc.joinery, i.e.,preparationofjoints isoneof the importantoperations inallwood
works.Itdealswiththespecificworkofcarpenterlikemakingdifferenttypesofjointstoformafinished
product.
2.2TIMBER
Timberisthenamegiventothewoodobtainedfromwellgrowntrees.Thetreesarecut,sawn
intovarioussizestosuitbuildingpurposes.
Theword,grain,asappliedtowood,referstotheappearanceorpatternofthewoodonthe
cutsurfaces.Thegrainofthewoodisafibrousstructureandtomake itstrong,thetimbermustbeso
cut,thatthegrainsrunparalleltothelength.
2.2.1Timbersizes
Timbersoldinthemarketisinvarioussizesandshapes.Thefollowingarethecommonshapes
andsizes.
a. Log Thetrunkofthetreewhichisfreefrombranches.
b. Balk Thelog,sawntohaveroughlysquarecrosssection.
c. Post Atimberpiece,roundorsquareincrosssection,havingitsdiameterorside
from175to300mm.
d. Plank Asawntimberpiece,withmorethan275mminwidth,50to150mmin
thicknessand2.5to6.5metersinlength.
e. Board Asawntimberpiece,below175mminwidthand30to50mminthickness.
f. Reapers Sawntimberpiecesofassortedandnonstandardsizes,whichdonotconfirm
totheaboveshapesandsizes.
2.2.2ClassificationofTimber
Wood suitable for construction and other engineering purposes is called timber.Woods in
generalaredividedintotwobroadcategories:SoftwoodsandHardwoods.
Softwoodsareobtainedfromconifers,kair,deodar,chir,walnutandseemal.Woodsobtainedfrom teak, sal,oak, shisham,beach, ashmango,neemandbabulare knownashardwood,but it ishighlydurable.
Another classification ofwoods isbasedon thenameof the trees like teak,babul, shisham,
neem,kair,chir,etc.
2.2.3SeasoningofWood
Anewlyfelledtreecontainsconsiderablemoisturecontent.Ifthisisnotremoved,thetimberis
likely towrap, shrink, crackordecay. Seasoning is the art of extracting themoisture contentunder
controlledconditions,atauniformrate,fromallthepartsofthetimber.Onlyseasonedwoodshouldbe
usedforallcarpentryworks.Seasoningmakesthewoodresilientandlighter.Further,itensuresthatthe
woodwillnotdistortafteritismadeintoanobject.
2.2.4CharacteristicsofGoodTimber
Thegoodtimbermustpossessthefollowingcharacteristics
a. Itshouldhaveminimummoisturecontent,i.e.,thetimbershouldbewellseasoned.
b. Thegrainsofwoodshouldbestraightandlong.
c. Itmustretainitsstraightnessafterseasoning.
d. Itshouldproducenearmetallicsoundonhammering.
e. Itshouldbefreefromknotsorcracks.
f. Itshouldbeofuniformcolor,throughoutthepartofthewood.
g. Itshouldrespondwelltothefinishingandpolishingoperations.
h. Duringdrivingthenailsandscrew,itshouldnotspliteasily.
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2.3MARKINGANDMEASURINGTOOLS
Accuratemarking andmeasurement is very essential in carpentrywork, toproduceparts to
exact size.To transferdimensionsonto thework; the followingare themarkingandmeasuring tools
thatarerequiredinacarpentryshop.
2.3.1SteelruleandSteeltape
Steelruleisasimplemeasuringinstrumentconsistingofalong,thinmetalstripwithamarked
scaleof
unit
divisions.
Itisan
important
tool
for
linear
measurement.
Steel
tape
isused
for
large
measurements,suchasmarkingonboardsandcheckingtheoveralldimensionsofthework.
Figure2.1:SteelruleandSteeltape2.3.2MarkinggaugeIt isa toolused tomark linesparallel to theedgeofawoodenpiece. Itconsistsofa square
woodenstemwithaslidingwooden stock (head)on it.On thestem is fittedamarkingpin,madeof
steel.Thestockissetatanydesireddistancefromthemarkingpointandfixedinpositionbyascrew.It
mustbeensured thatthemarkingpinprojects throughthestem,about3mmandtheendaresharp
enoughtomakeaveryfineline.Amortisegaugeconsistsoftwopins.Inthis,itispossibletoadjustthedistancebetweenthepins,todrawtwoparallellinesonthestock.
a.Markinggauge b.MortisegaugeFigure2.2:Markinggauges
2.3.3Trysquare
Itisusedformarkingandtestingthesquarenessandstraightnessofplanedsurfaces.Itconsists
ofasteelblade,fittedinacastironstock.Itisalsousedforcheckingtheplanedsurfacesforflatness.Its
sizevariesfrom150to300mm,accordingtothelengthoftheblade.Itislessaccuratewhencompared
tothetrysquareusedinthefittingshop.
Figure2.3:Trysquare
2.3.4Compassanddivider
Compassanddivider,areusedformarkingarcsandcirclesontheplanedsurfacesofthewood.
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2.3.5Scriberormarkingknife
It isusedformarkingontimber.It ismadeofsteelhavingoneendpointedandtheotherend
formedintoasharpcuttingedge.
2.3.6BevelIt isused for layingoutandcheckingangles.Thebladeof thebevel isadjustableandmaybe
heldinplacebyathumbscrew.Afteritissettothedesiredangle,itcanbeusedinmuchthesameway
asatry
square.
Agood
way
to
set
itto
the
required
angle
isto
mark
the
angle
on
asurface
and
then
adjustthebladetofittheangle.
Figure2.4:CompassandDivider Figure2.5:ScriberandBevel
2.4HOLDINGTOOLS2.4.1Carpenter'svice
Figure2.6showsthecarpenter'sbenchvice,usedasaworkholdingdeviceinacarpentershop.
Itsonejawisfixedtothesideofthetablewhiletheotherismovablebymeansofascrewandahandle.
TheCarpenter'svicejawsarelinedwithhardwooden'faces.
Figure2.6:Carpentersvice Figure2.7:Cclamp
2.4.2Cclamp
Figure2.7showsaCclamp,whichisusedforholdingsmallworks.
2.4.3Barcramp
Figure2.8showsabarcramp. It ismadeofsteelbarofTsection,withmalleable iron fittings
andasteelscrew.Itisusedforholdingwideworkssuchasframesortops.
Figure2.8:barcramp
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2.5PLANINGTOOLSPlaningistheoperationusedtoproduceflatsurfacesonwood.Aplane isahandtoolusedfor
thispurpose.Thecuttingbladeusedinaplaneisverysimilartoachisel.Thebladeofaplaneisfittedin
awoodenormetallicblock,atanangle.
2.5.1JackplaneIt is themostcommonlyusedgeneralpurposeplane. It isabout35cm long.Thecutting iron
(blade)should
have
acutting
edge
of
slight
curvature.
Itisused
for
quick
removal
of
material
on
rough
workandisalsousedinobliqueplanning.
2.5.2Smoothingplane
Itisusedforfinishingworkandhence,thebladeshouldhaveastraightcuttingedge.Itisabout
20to25cmlong.Beingshort,itcanfolloweventheslightdepressionsinthestock,betterthanthejack
plane.Itisusedafterusingthejackplane.
2.5.3Rebateplane
Itisusedformakingarebate.Arebateisarecessalongtheedgeofapieceofwood,whichis
generallyusedforpositioningglassinframesanddoors.
2.5.4Plough
plane
It isusedtocutgrooves,whichareusedtofixpanels inadoor.Figure2.9showsthevarious
typesofplanesmentionedabove.
Figure2.9:Typesofplanes
2.6CUTTINGTOOLS
2.6.1SawsA saw is used to cutwood into pieces. There are different types of saws, designed to suit
differentpurposes.Asawisspecifiedbythelengthofitstoothededge.
2.6.1.1Crosscutorhandsaw
It isused tocutacross thegrainsof thestock.The teetharesoset that thesawkerfwillbe
widerthanthebladethickness.Thisallowsthebladetomovefreelyinthecut,withoutsticking.
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2.6.1.2Ripsaw
It isusedforcuttingthestockalongthegrains.Thecuttingedgeofthissawmakesasteeper
angle,i.e.,about60whereasthatofcrosscutsawmakesanangleof45withthesurfaceofthestock.
2.6.1.3Tenonsaw
Itisusedforcuttingthestockeitheralongoracrossthegrains.Itisusedforcuttingtenonsand
infinecabinetwork.However,itisusedforsmallandthincuts.Thebladeofthissawisverythinandso
itisstiffened
with
athick
back
steel
strip.
Hence,
this
issometimes
called
as
back
saw.
In
this,
the
teeth
areshapedlikethoseofcrosscutsaw.
2.6.1.4Compasssaw
Ithasanarrow,longerandstrongertaperingblade,whichisusedforheavyworks(Fig.1.13).It
ismostlyusedinradiuscutting.Thebladeofthissawisfittedwithanopentypewoodenhandle.
Figure2.10:Typesofsaws
2.6.2Chisels
Chiselsareused for cuttingand shapingwoodaccurately.Wood chiselsaremade in various
bladewidths, ranging from3 to50mm.Theyarealsomade indifferentblade lengths.Mostof the
woodchiselsaremadeintotangtype,havingasteelshankwhichfitsinsidethehandle.Thesearemade
offorgedsteelortoolsteelblades.
Figure2.11:Partsofchisel
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2.6.2.1Firmerchisel
Theword'firmer'means'stronger'andhencefirmerchiselisstrongerthanotherchisels.Itisa
generalpurposechiselandisusedeitherbyhandpressureorbyamallet.Thebladeofafirmerchiselis
flat,asshowninFigure2.12a.
2.6.2.2Dovetailchisel
Ithasabladewithabeveledback,asshowninFigure,duetowhichitcanentersharpcomers
forfinishing,
as
in
dovetail
joints.
2.6.2.3Mortisechisel
It isusedforcuttingmortisesandchipping insideholes,etc.Thecrosssectionofthemortisechisel is
proportioned towithstandheavyblowsduringmortising.Further, thecrosssection ismade stronger
neartheshank.
a.Firmer b.Dovetail c.MortiseFigure2.12: Typesofchisels
2.7 DRILLINGANDBORINGTOOLS2.7.1Carpentersbrace
It isused forrotatingaugerbits, twistdrills,etc., toproduceholes inwood. Insomedesigns,
braces are made with ratchet device.With this, holesmay bemade in a corner where complete
revolutionofthehandlecannotbemade.Thesizeofabraceisdeterminedbyitssweep.
2.7.2AugerbitIt isthemostcommontoolused formakingholes inwood.Duringdrilling,the leadscrewof
thebitguides intothewood,necessitatingonlymoderatepressureonthebrace.Thehelicalfluteson
thesurfacecarrythechipstotheoutersurface.
2.7.3HanddrillCarpenter's brace is used tomake relatively large size holes;whereashand drill isused for
drillingsmallholes.Astraightshankdrill isusedwith this tool. It issmall, light inweightandmaybe
convenientlyused than thebrace.Thedrillbit isclamped in thechuckat itsendand is rotatedbya
handleattachedtogearandpinionarrangement.
2.7.4Gimlet
Ithascuttingedges likea twistdrill. It isused fordrilling largediameterholeswith thehand
pressure.
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Figure2.13: Drillingtools
2.8MISCELLANEOUS
TOOLS
2.8.1MalletItisusedtodrivethechisel,whenconsiderableforceistobeapplied,whichmaybethecasein
makingdeeproughcuts.Steelhammershouldnotbeusedforthepurpose,asitmaydamagethechisel
handle.Further,forbettercontrol,itisbettertoapplyaseriesoflighttapswiththemalletratherthana
heavysingleblow.
2.8.2PincerIt ismadeof two forgedsteelarmswithahingedjointand isused forpullingoutsmallnails
fromwood.Theinnerfacesofthepincerjawsarebeveledandtheouterfacesareplain.Theendofone
armhasaballandtheotherhasaclaw.Thebeveledjawsandtheclawareusedforpullingoutsmall
nails,pinsandscrewsfromthewood.
2.8.3ClawhammerIthasastrikingflatfaceatoneendand theclawattheother,asshown in figure.Theface is
usedtodrivenailsintowoodandforotherstrikingpurposesandtheclawforextractingrelativelylarge
nailsoutofwood.Itismadeofcaststeelandweighsfrom0.25kgto0.75kg.
2.8.4Screwdriver
Itisusedfordrivingscrews intowoodorunscrewingthem.Thescrewdriverofacarpenter is
differentfromtheothercommontypes,asshowninfigure.
The length of a screw driver is determined by the length of the blade. As the length of the blade
increases,thewidthandthicknessofthetipalsoincrease.
2.8.5WoodraspfileIt isa finishingtoolusedtomakethewoodsurfacesmooth,removesharpedges, finishfilletsandotherinteriorsurfaces.Sharpcuttingteethareprovidedonits
surfaceforthepurpose.Thisfileisexclusivelyusedinwoodwork.
2.8.6BradawlItisahandoperatedtool,usedtoboresmallholesforstartingascreworlargenail.
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a.Mallet b.Pincer c.Clawhammer d.Bradawl
e.Woodraspfile f.Screwdriver
Figure2.14:Miscellaneoustools
2.9WOODJOINTS
Therearemanykindsofjointsused toconnectwoodstock.Eachjointhasadefiniteuseand
requires lay inout,cutting them together.Thestrengthof thejointdependsuponamountofcontactarea.Ifaparticularjointdoesnothavemuchcontactarea,thenitmustbereinforcedwithnails,screws
ordowels.Thefigure2.15showssomecommonlyusedwoodjoints.
a.Butt b.Dowell c.Dado d.Rabbet
e.Lap f.Mortiseandtenon g.Miter
Figure2.15: Commonwoodjoints
2.9.1Lapjoints
Inlapjoints,anequalamountofwoodisremovedfromeachpiece,asshowninfigure2.16.Lap
jointsareeasyto layout,usingatrysquareandamarkinggauge.Followtheproceduresuggestedfor
sawingandremovingthewastestock.Ifthejointisfoundtobetootight,itisbettertoreducethewidth
of thematingpiece, insteadof trimming theshoulderof thejoint.This typeofjoint isused forsmall
boxestolargepiecesoffurniture.
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Figure2.16:Lapjoints
2.9.2MortiseandTenonJoints
It is used in the construction of quality furniture. It results in a strong joint and requires
considerableskilltomakeit.Thefollowingarethestagesinvolvedinthework.
a. Markthemortiseandtenonlayouts.
b. Cutthemortisefirstbydrillingseriesofholeswithinthe layout line,chiselingoutthewastestock
andtrimmingthecornersandsides.
c. Preparethetenonbycuttingandchiseling.
d. Checkthetenonsizeagainstthemortisethathasbeenpreparedandadjustitifnecessary.
Figure2.17:Mortiseand Tenonjoints
2.9.3Bridlejoint
Thisisthereverseofmortiseandtenonjointinform.Themarkingoutofthejointisthesameas
formortiseandtenonjoint.Thisjointisusedwherethemembersareofsquareornearsquaresection
andunsuitableformortiseandtenonjoint.
Figure2.18: Bridlejoint
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2.10SAFEPRACTICE
Thefollowingaresomeofthesafeandcorrectworkpracticesincarpentryshop,withrespectto
thetoolsused
1. Toolsthatarenotbeingusedshouldalwaysbekeptattheirproperplaces.
2. Makesurethatyourhandsarenotinfrontofsharpedgedtoolswhileyouareusingthem.
3. Useonlysharptools.Adulltoolrequiresexcessivepressure,causingthetooltoslip.
4. Woodenpieceswithnails,shouldneverbeallowedtoremainonthefloor.
5. Becareful
when
you
are
using
your
thumb
as
aguide
in
cross
cutting
and
ripping.
6. Testthesharpnessofthecuttingedgeofchiselonwoodorpaper,butnotonyourhand.
7. Neverchiseltowardsanypartofthebody.
8. Donotusechiselswherenailsarepresent.Donotusechiselasascrewdriver.
9. Donotuseasawwithaloosehandle.
10.Alwaysusetriangularfileforsharpeningtheteeth.
11.Donotuseasawonmetallicsubstances.
12.Donotusemallettostrikenails.
13.Donotuseplaneattheplaces,whereanailisdriveninthewood.
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ME101WorkshopPracticeI Carpentry
Exercise1TLapjoint
Aim
TomakeaTlapjointasshowninFigure2.19,fromthegivenreaperofsize50x35x250mm.Toolsrequired
Carpenter'svice,steelrule,jackplane, trysquare,markinggauge,25mm firmerchisel,crosscutsaw,
tenonsaw,scriberandmallet.
Sequenceofoperations
1. Thegivenreaperischeckedtoensureitscorrectsize.
2. Thereaper isfirmlyclamped inthecarpenter'sviceandanytwoadjacentfacesareplanedbythe
jackplaneandthetwofacesarecheckedforsquarenesswiththetrysquare.
3. Markinggaugeissetandlinesaredrawnat30and45mm,tomarkthethicknessandwidthofthe
modelrespectively.
4. Theexcessmaterialisfirstchiseledoutwithfirmerchiselandthenplanedtocorrectsize.
5. ThematingdimensionsofthepartsXandYarethenmarkedusingscaleandmarkinggauge
6. Usingthecrosscutsaw,theportionstoberemovedarecutinboththepieces,followedbychiselingandalsothepartsXandYareseparatedbycrosscutting,usingthetenonsaw
7. Theendsofboththepartsarechiseledtotheexactlengths.
8. Afinefinishingisgiventotheparts,ifrequiredsothat,properfittingisobtained.
9. Thepartsarefittedtoobtainaslightlytightjoint.
Result TheTLapjointisthusmadebyfollowingtheabovesequenceofoperations.
FigureC E1: T lapjoint
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ME101WorkshopPracticeI Carpentry
Exercise2Dovetaillapjoint
Aim
TomakeadovetaillapjointasshowninFigure2.20,fromthegivenreaperofsize50x35x250mm.Toolsrequired
Carpentersvice,steelrule,jackplane,trysquare,markinggauge,25mm firmerchisel,crosscutsaw,
tenonsaw,scriberandmallet.
Sequenceofoperations
1. Thegivenreaperischeckedtoensureitscorrectsize.
2. Thereaper isfirmlyclamped inthecarpenter'sviceandanytwoadjacentfacesareplanedbythe
jackplaneandthetwofacesarecheckedforsquarenesswiththetrysquare.
3. Markinggaugeissetandlinesaredrawnat30anc145mm,tomarkthethicknessandwidthofthe
modelrespectively.
4. Theexcessmaterialisfirstchiseledoutwithfirmerchiselandthenplanedtocorrectsize.
5. ThematingdimensionsofthepartsXandYarethenmarkedusingscaleandmarkinggauge.
6. Usingthecrosscutsaw,theportionstoberemovedarecutinboththepieces,followedbychiselingandalsothepartsXandYareseparatedbycrosscutting,usingthetenonsaw.
7. Theendsofboththepartsarechiseledtoexactlengths.
8. Afinefinishingisgiventotheparts,ifrequiredsothat,properfittingisobtained.
9. Thepartsarefittedtoobtainaslightlytightjoint.
Result Thedovetaillapjointisthusmadebyfollowingtheabovesequenceofoperations.
FigureC E2:Dovetaillapjoint
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ME101WorkshopPracticeI Carpentry
Exercise3MortiseandTenonjoint
Aim
TomakeamortiseandtenonjointasshowninFig.1.34b,fromthegivenreaperofsize50x35x250mm.
Toolsrequired
Carpenter'svice,steelrule,jackplane,trysquare,markinggauge,25111mfirmerchisel,6mmmortisechisel,crosscutsaw,tenonsaw,scriberandmallet.
Sequenceofoperations
1. Thegivenreaperischeckedtoensureitscorrectsize.
2. Thereaperisfirmlyclampedinthecarpenter'sviceandoneofitsfacesareplanedbythejackplane
andcheckedforstraightness.
3. Theadjacentfaceisthenplanedandthefacesarecheckedforsquarenesswiththetrysquare.
4. Markinggaugeissetandlinesaredrawnat30and45mm,tomarkthethicknessandwidthofthe
modelrespectively.
5. Theexcess
material
isfirst
chiseled
out
with
the
firmer
chisel
and
then
planed
to
correct
size.
6. ThematingdimensionsofthepartsXandYarethenmarkedusingthescaleandmarkinggauge.
7. Usingthecrosscutsaw,theportionstoberemovedinpartY(tenon)iscut,followedbychiseling.
8. ThematerialtoberemovedinpartX(mortise)iscarriedoutbyusingthemortise
andfirmerchisels.
9. ThepartsXandYareseparatedbycrosscuttingwiththetenonsaw
10.Theendsofboththepartsarechiseledtoexactlengths.
11.Finishchiselingisdonewhereverneededsothat,thepartscanbefittedtoobtainaneartightjoint.
Result Themortiseandtenonjointisthusmadebyfollowingtheabovesequenceofoperations.
FigureCE3: MortiseandTenonjoint
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Chapter3
WELDING
3.1 INTRODUCTION
Welding is the process ofjoining similarmetals by the application of heat,with orwithout
applicationofpressureor fillermetal, in such away that thejoint is equivalent in composition and
characteristicsofthemetalsjoined.Inthebeginning,weldingwasmainlyusedforrepairingallkindsofwornordamagedparts.Now, it is extensivelyused inmanufacturing industry, construction industry
(constructionof ships, tanks, locomotivesandautomobiles)andmaintenancework, replacing riveting
andbolting,toagreaterextent.
Thevariousweldingprocessesare:
1. Electricarcwelding,
2. Gaswelding
3. Thermalwelding
4. ElectricalResistanceweldingand
5. Frictionwelding
However,onlyelectricarcweldingprocessisdiscussedinthesubjectpointofview.
3.2ELECTRICARCWELDING
Arcweldingistheweldingprocess,inwhichheatisgeneratedbyanelectricarcstruckbetweenanelectrodeand theworkpiece.Electricarc is luminouselectricaldischargebetween twoelectrodes
throughionizedgas.
Figure3.1:Arcweldingsetup.
Anyarcweldingmethodisbasedonanelectriccircuitconsistingofthefollowingparts:
a. Powersupply(ACorDC);b. Weldingelectrode;c. Workpiece;
d. Weldingleads(electriccables)connectingtheelectrodeandworkpiecetothepowersupply.Electric arc between the electrode and work piece closes the electric circuit. The arc
temperaturemayreach10000F(5500C),whichissufficientforfusiontheworkpieceedgesandjoining
them. Whena longjoint isrequiredthearc ismovedalongthejoint line.The frontedgeoftheweld
poolmeltstheweldedsurfaceswhentherearedgeoftheweldpoolsolidifiesformingthejoint.
Transformers,motor generators and rectifiers sets areused as arcweldingmachines. These
machinessupplyhighelectriccurrentsatlowvoltageandanelectrodeisusedtoproducethenecessary
arc.Theelectrodeservesasthefillerrodandthearcmeltsthesurfacesothat,themetalstobejoined
areactuallyfixedtogether.
Sizesofweldingmachinesareratedaccordingtotheirapproximateamperagecapacityat60%
duty cycle, such as 150,200,250,300,400,500 and 600 amperes. This amperage is the rated current
outputattheworkingterminal.
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3.2.1Transformers
The transformers typeofweldingmachineproducesA.C currentand isconsidered tobe the
leastexpensive.Ittakespowerdirectlyfrompowersupplylineandtransformsittothevoltagerequired
forwelding.Transformersareavailableinsinglephaseandthreephasesinthemarket.
3.2.2Motorgenerators
TheseareD.Cgeneratorssets,inwhichelectricmotorandalternatoraremountedonthesame
shaft toproduceD.Cpoweraspert the requirement forwelding.Thesearedesigned toproduceD.C
currentin
either
straight
or
reversed
polarity.
The
polarity
selected
for
welding
depends
upon
the
kind
ofelectrodeusedandthematerialtobewelded.
3.2.3Rectifiers
Theseareessentiallytransformers,containinganelectricaldevicewhichchangesA.CintoD.Cby
virtueofwhichtheoperatorcanusebothtypesofpower(A.CorD.C,butonlyoneatatime).Inaddition
totheweldingmachine,certainaccessoriesareneededforcarryingouttheweldingwork.
3.2.4Weldingcables
Twowelding cables are required, one frommachine to the electrodeholder and theother,
fromthemachinetothegroundclamp.Flexiblecablesareusuallypreferredbecauseofthecaseofusing
andcoilingthecables.Cablesarespecifiedbytheircurrentcarryingcapacity,say300A,400A,etc.
3.2.5Electrodes
Fillerrodsareusedinarcweldingarecalledelectrodes.Thesearemadeofmetallicwirecalled
corewire,
having
approximately
the
same
composition
as
the
metal
to
be
welded.
These
are
coated
uniformlywithaprotectivecoatingcalledflux.Whilefluxinganelectrode;about20mmoflengthisleft
atoneendforholding itwiththeelectrodeholder. Ithelps intransmittingfullcurrentfromelectrode
holdertothefrontendoftheelectrodecoating.Fluxactsasan insulatorofelectricity.Figure.4shows
thevariouspartsofanelectrode.
Figure3.2:Partsofanelectrode
Ingeneral,electrodesareclassifiedintofivemaingroups;mildsteel,carbonsteel,specialalloy
steel,cast ironandnonferrous.Thegreatestrangeofarcwelding isdonewithelectrodes inthemild
steelgroup.
Variousconstituents liketitaniumoxide,potassiumoxide,cellulose, ironormanganese,Ferro
silicates,carbonates,gums,clays,asbestos,etc.,areusedascoatingsonelectrodes.Whilewelding,the
coatingorfluxvaporizesandprovidesagaseousshieldtopreventatmosphericattack.
ThesizeofelectrodeismeasuredanddesignatedbythediameterofthecorewireinSWGand
length,apartfromthebrandandcodenames;indicatingthepurposeforwhichtherearemostsuitable.Electrodesmaybeclassifiedonthebasisofthicknessofthecoatedflux.As
1. Dustcoatedorlightcoated
2. Semiormediumcoatedand
3. Heavilycoatedorshielded
Electrodesarealsoclassifiedonthebasisofmaterials,as
1. Metallicand
2. Nonmetallicorcarbon
Metallicarcelectrodesarefurthersubdividedinto
1. Ferrousmetalarcelectrode(mildsteel,low/medium/highcarbonsteel,castiron,stainlesssteel,etc)
2. Nonferrousmetalarcelectrodes(copper,brass,bronze,aluminum,etc).
Incaseofnonmetallicarcelectrodes,mainlycarbonandgraphiteareusedtomaketheelectrodes.
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3.3WELDINGTOOLS
3.3.1Electrodeholder
Theelectrodeholder isconnected to theendof theweldingcableandholds theelectrode. It
shouldbelight,strongandeasytohandleandshouldnotbecomehotwhileinoperation.Figureshows
one typeof electrodeholder.Thejawsof theholder are insulated,offeringprotection fromelectric
shock.
Figure3.3:Electrodeholder Figure3.4:Groundclamp
3.3.2Groundclamp
Itisconnectedtotheendofthegroundcableandisclampedtotheworkorweldingtabletocompletetheelectriccircuit.Itshouldbestronganddurableandgivealowresistanceconnection.
3.3.3Wirebrushandchippinghammer
Awirebrushisusedforcleaningandpreparingtheworkforwelding.Achippinghammerisused
forremovingslagformationonwelds.Oneendoftheheadissharpenedlikeacoldchiselandtheother,
toablunt,roundpoint. It isgenerallymadeoftoolsteel.Moltenmetaldispersedaroundthewelding
heads,intheformofsmalldrops,isknownasspatter.Whenafluxcoatedelectrodeisusedinwelding
process,thenalayeroffluxmaterial isformedovertheweldingbeadwhichcontainstheimpuritiesof
weldmaterial.This layer isknownas slag.Removing the spatterandslag formedonandaround the
weldingbeadsonthemetalsurfaceisknownaschipping.
Figure3.5:Wirebrush Figure3.6:Chippinghammer
3.3.4Weldingtableandcabin
It ismadeofsteelplateandpipes. It isused forpositioning theparts tobeweldedproperly.
Weldingcabinismadeupbyanysuitablethermalresistancematerial,whichcanisolatethesurrounding
bytheheatandlightemittedduringtheweldingprocess.Asuitabledraughtshouldalsobeprovidedforexhaustingthegasproducedduringwelding.
3.3.5Faceshield
Afaceshield isusedtoprotecttheeyesandfacefromtheraysofthearcandfromspatteror
flyingparticlesofhotmetal.Itisavailableeitherinhandorhelmettype.Thehandtypeisconvenientto
usewherevertheworkcanbedonewithonehand.Thehelmettypethoughnotcomfortabletowear,
leavesbothhandsfreeforthework.
Shieldsaremadeoflightweightnonreflectingfiberandfittedwithdarkglassestofilteroutthe
harmfulraysofthearc.Insomedesigns,acoverglassisfittedinfrontofthedarklenstoprotectitfrom
spatter.
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3.3.6Handgloves
Theseareusedtoprotectthehandsfromelectricshocksandhotspatters
Handheldtype Helmettype
Figure3.7:Handgloves Figure3.8:Faceshield
3.4TECHNIQUESOFWELDING
3.4.1Preparationofwork
Beforewelding, theworkpiecesmustbe thoroughly cleanedof rust, scaleandother foreign
material.Thepieceformetalgenerallyweldedwithoutbevelingtheedges,however,thickworkpiece
shouldbebeveledorveedouttoensureadequatepenetrationandfusionofallpartsoftheweld.But,in
eithercase,thepartstobeweldedmustbeseparatedslightlytoallowbetterpenetrationoftheweld.
Beforecommencingtheweldingprocess,thefollowingmustbeconsidered
a) Ensurethattheweldingcablesareconnectedtoproperpowersource.
b) Settheelectrode,asperthethicknessoftheplatetobewelded.
c) Settheweldingcurrent,asperthesizeoftheelectrodetobeused.
Table3.1ElectrodecurrentVselectrodesizeVsplatethickness.
Platethickness,mm Electrodesize,mm Electrodecurrentrange,amp
1.6
2.5
4.0
6.0
8.0
25.0
1.6
2.5
3.2
4.0
5.0
6.0
4060
5080
90130
120170
180270
300400
NOTE:Whilemakingbuttweldsinthinmetal,itisabetterpracticetotackweldthepiecesintervalsto
holdthemproperlywhilewelding.
3.4.2Strikinganarc
Thefollowingarethestagesandmethodsofstrikinganarcandrunninga beada) Selectanelectrodeofsuitablekindandsize fortheworkandset theweldingcurrentataproper
value.
b) Fastenthegroundclamptoeithertheworkorweldingtable.
c) Startorstrikethearcbyeitherofthefollowingmethods
Strikeandwithdraw
Inthismethodthearcisstartedbymovingtheendoftheelectrodeontotheworkwithaslow
sweepingmotion,similartostrikingamatch.
Touchandwithdraw
Inthismethod,thearcisstartedbykeepingtheelectrodeperpendicularto theworkand
touchingorbouncingitlightlyonthework.Thismethodispreferredasitfacilitatesrestartingthe
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momentarilybrokenarcquickly. Iftheelectrodestickstothework,quicklybenditbackandforth,
pullingatthesametime.Makesuretokeeptheshieldinfrontoftheface,whentheelectrodeis
freedfromsticking.
d) Assoonasthearc isstruck,movetheelectrodealong,slowlyfrom lefttoright,keepingat15to
25fromverticalandinthedirectionofwelding.
Strikeandwithdraw Touchandwithdraw
Figure3.9: strikinganarc
3.4.3Weaving
A steady,uniformmotionof the electrodeproduces a satisfactorybead.However, a slight
weavingoroscillatingmotionispreferred,asthiskeepsthemetalmoltenalittlelongerandallowsthe
gas to escape, bringing the slag to the surface. Weaving also produces a wider bead with better
penetration.
3.5TYPESOFJOINTS
Weldsaremadeatthejunctionofthevariouspiecesthatmakeuptheweldment.Thejunctions
ofparts,orjoints,aredefinedasthelocationwheretwoormorenumbersaretobejoined.Partsbeing
joinedtoproducetheweldmentmaybe intheformofrolledplate,sheet,pipes,castings,forgings,or
billets.Thefivebasictypesofjointsarelistedbelow.
Figure3.10: Typesofweldingjoints.
Abuttjointisusedtojointwomembersalignedinthesameplane(fig.3.10,viewA).Thisjointis
frequently used in plate, sheetmetal, and pipework. Ajoint of this typemay be either square or
grooved.
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Cornerandteejointsareusedtojoin twomembers locatedatrightanglestoeachother(fig.
3.10,viewsBandC).Incrosssection,thecornerjointformsanLshape,andtheteejointhastheshape
oftheletterT.Variousjointdesignsofbothtypeshaveusesinmanytypesofmetalstructures.
Alapjoint,asthename implies,ismadebylappingonepieceofmetaloveranother(fig.3.10,
viewD).Thisisoneofthestrongesttypesofjointsavailable;however,formaximumjointefficiency,you
shouldoverlap themetalsaminimumof three times the thicknessof the thinnestmember you are
joining.Lapjointsarecommonlyusedwithtorchbrazingandspotweldingapplications.
Anedge
joint
isused
to
join
the
edges
of
two
or
more
members
lying
in
the
same
plane.
In
most
cases,oneofthemembersisflanged,asshowninfigure3.10,viewE.Whilethistypeofjointhassome
applicationsinplatework,itismorefrequentlyusedinsheetmetalwork. Anedgejointshouldonlybe
usedforjoiningmetals1/4inchorlessinthicknessthatarenotsubjectedtoheavyloads.
3.6WELDINGPOSITIONS
Dependingupon the locationof theweldingjoints,appropriatepositionof theelectrodeand
handmovementisselected.Thefigureshowsdifferentweldingpositions.
Figure3.11: Weldingpositions
3.6.1Flatpositionwelding
Inthisposition,theweldingisperformedfromtheuppersideofthejoint,andthefaceoftheweld
is approximately horizontal. Flat welding is the preferred term; however, the same position is
sometimescalleddownhand.
3.6.2Horizontalpositionwelding
In thisposition,welding isperformedon theuppersideofanapproximatelyhorizontalsurface
andagainstanapproximatelyverticalsurface.
3.6.3Verticalpositionwelding
Inthisposition,theaxisoftheweldisapproximatelyverticalasshowninfigure.
3.6.4Overheadpositionwelding
Inthisweldingposition,theweldingisperformedfromtheundersideofajoint.
3.7 ADVANTAGES&DISADVANTAGESOFARCWELDING
Advantages
1.Weldingprocessissimple.
2. Equipmentisportableandthecostisfairlylow.
3. Alltheengineeringmetalscanbeweldedbecauseoftheavailabilityofawidevarietyofelectrodes.
Disadvantages
1. Mechanizedweldingisnotpossiblebecauseoflimitedlengthoftheelectrode.
2. Numberofelectrodesmayhavetobeusedwhileweldinglongjoints.
3. Adefect(slaginclusionorinsufficientpenetration)mayoccurattheplacewhereweldingisrestarted
withafreshelectrode.
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3.8SAFEPRACTICE
Alwaysweld inawellventilatedplace.Fumesgivenofffromweldingareunpleasantand insome
casesmaybeinjurious,particularlyfromgalvanizedorzinccoatedparts.
1. Donotweldaroundcombustibleorinflammablematerials,wheresparksmaycauseafire.
2. Neverweldcontainers,whichhavebeenusedforstoringgasoline,oilorsimilarmaterials,without
firsthavingthemthoroughlycleaned.
3. Check theweldingmachine tomake sure that it isproperlygroundedand thatall leadsproperly
insulated.
4. Never lookatthearcwiththenakedeye.Thearccanburnyoureyesseverely.Alwaysusea face
shieldwhilewelding.
5. Preventweldingcablesfromcomingincontactwithhotmetal,water,oil,orgrease.Avoiddragging
thecablesaroundsharpcorners.
6. Ensureproperinsulationofthecablesandcheckforopenings.
7. Alwayswearthesafetyhandgloves,apronandleathershoes.
8. Alwaysturnoffthemachinewhenleavingthework.
9. Applyeyedropsafterweldingisoverfortheday,torelievethestrainontheeyes.
10.Whilewelding,standondryfootingandkeepthebodyinsulatedfromtheelectrode,anyotherparts
oftheelectrodeholderandthework.
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ME101WorkshopPracticeI Welding
Exercise1SingleV Buttjoint
Aim
Tomakeasinglevbuttjoint,usingthegivenmildsteelpiecesof andbyarcwelding.Materialused
Twomildsteelpiecesof100X40X6mm.
Toolsandequipmentused
Arcweldingmachine,Mildsteelelectrodes,Electrodeholder,Groundclamp,flatnoseTong,Faceshield,
Apron,Handgloves,MetallicworkTable,Benchvice,Roughflatfile,Trysquare,Steelrule,Wirebrush,
Ballpeenhammer,Chippinghammer,ChiselandGrindingmachine.
Sketch
Figure3.12: SingleVbuttjoint
Operationstobecarriedout
1. Cleaningtheworkpieces
2. tackwelding
3. fullwelding
4. cooling
5. chipping
6. finishing
Procedure
1. Takethetwomildsteelpiecesofgivendimensionsandcleanthesurfacesthoroughlyfromrust,dust
particles,oilandgrease.
2. Removethesharpcornersandburrsbyfilingorgrinding.
3. Oneedgeofeachpieceisbeveled,toanangle30.
4. Thetwopiecesarepositionedontheweldingtablesuchthat,theyareseparatedslightlyforbetter
penetrationoftheweld.
5. Theelectrodeisfittedintotheelectrodeholderandtheweldingcurrentissettoapropervalue.
6. Thegroundclampisfastenedtotheweldingtable.ThemachineisswitchedON
7. Wearingtheapron,handgloves,usingthefaceshield,thearcisstruckandtheworkpiecesaretack
weldedattheendsandholdingthetwopiecestogether;firstrunoftheweldisdonetofilltheroot
gap.
8. Secondrunoftheweldingisdonewithproperweavingandwithuniformmovement.Duringthe
processofwelding,theelectrodeiskeptatangleof15to25fromverticalandinthedirectionof
welding.
9. Theslagformationontheweldisremovedbychippinghammer.
10.Filingisdonetoremovespattersaroundtheweld.
Result Thesinglevbuttjointisthusmade,usingthetoolsandequipmentasmentionedabove.
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ME101WorkshopPracticeI Carpentry
Exercise2Double Lapjoint
Aim
Tomakeadoublelapjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused
Twomildsteelpiecesof100X40X6mm.
Toolsandequipmentused
Arcweldingmachine,Mildsteelelectrodes,Electrodeholder,Groundclamp,flatnoseTong,Faceshield,
Apron,Handgloves,MetallicworkTable,Benchvice,Roughflatfile,Trysquare,Steelrule,Wirebrush,
Ballpeenhammer,Chippinghammer,ChiselandGrindingmachine.
Sketch
Figure3.13: Doublelapjoint
Operationstobecarriedout
1. Cleaningtheworkpieces
2. tackwelding
3. fullwelding
4. cooling5. chipping
6. finishing
Procedure
1. Takethetwomildsteelpiecesofgivendimensionsandcleanthesurfacesthoroughlyfromrust,dust
particles,oilandgrease.
2. Removethesharpcornersandburrsbyfilingorgrindingandpreparetheworkpieces.
3. Theworkpiecesarepositionedontheweldingtable,toformalapjointwiththerequiredover
lapping.
4. Theelectrodeisfittedintotheelectrodeholderandtheweldingcurrentissettoapropervalue.
5. Thegroundclampisfastenedtotheweldingtable.
6. Wearingtheapron,handgloves,usingthefaceshieldandholdingtheoverlappedpiecesthearcis
struckandtheworkpiecesaretackweldedattheendsof boththesides7. Thealignmentofthelapjointischeckedandthetackweldedpiecesarereset,ifrequired.
8. Weldingisthencarriedoutthroughoutthelengthofthelapjoint,onboththesides.
9. Removetheslag,spattersandcleanthejoint.
Result Thedoublelapjointisthusmade,usingthetoolsandequipmentasmentionedabove.
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ME101WorkshopPracticeI Carpentry
Exercise3Cornerjoint
Aim
Tomakeacornerjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused
Twomildsteelpiecesof100X40X6mm.
Toolsandequipmentused
Arcweldingmachine,Mildsteelelectrodes,Electrodeholder,Groundclamp,flatnoseTong,Faceshield,
Apron,Handgloves,MetallicworkTable,Benchvice,Roughflatfile,Trysquare,Steelrule,Wirebrush,
Ballpeenhammer,Chippinghammer,ChiselandGrindingmachine.
Sketch
Figure3.14: Cornerjoint
Operationstobecarriedout
1. Cleaningtheworkpieces
2. tackwelding
3. fullwelding
4. cooling
5. chipping
6. finishing
Procedure
1. Takethetwomildsteelpiecesofgivendimensionsandcleanthesurfacesthoroughlyfromrust,dust
particles,oilandgrease.
2. Removethesharpcornersandburrsbyfilingorgrindingandpreparetheworkpieces.
3. Theworkpiecesarepositionedontheweldingtablesuchthat,theLshapeisformed.
4. Theelectrodeisfittedintotheelectrodeholderandtheweldingcurrentissettoapropervalue.
5. Thegroundclampisfastenedtotheweldingtable.
6. Wearingtheapron,handgloves,usingthefaceshieldandholdingthepiecesthearcisstruckand
theworkpiecesaretackweldedatboththeends.
7. Thealignmentofthecornerjointischeckedandthetackweldedpiecesarereset,ifrequired.
8. Weldingisthencarriedoutthroughoutthelength.
9. Removetheslag,spattersandcleanthejoint.
Result TheCornerjointisthusmade,usingthetoolsandequipmentasmentionedabove.
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ME101WorkshopPracticeI Carpentry
Exercise4Tjoint
Aim
TomakeaTjoint,usingthegivenmildsteelpiecesandbyarcwelding.Materialused
Twomildsteelpiecesof100X40X6mm.
Toolsandequipmentused
Arcweldingmachine,Mildsteelelectrodes,Electrodeholder,Groundclamp,flatnoseTong,Faceshield,
Apron,Handgloves,MetallicworkTable,Benchvice,Roughflatfile,Trysquare,Steelrule,Wirebrush,
Ballpeenhammer,Chippinghammer,ChiselandGrindingmachine.
Sketch
Figure3.15: Tjoint
Operationstobecarriedout
1. Cleaningtheworkpieces
2.tackwelding
3. fullwelding
4. cooling
5. chipping
6. finishing
Procedure
1. Takethetwomildsteelpiecesofgivendimensionsandcleanthesurfacesthoroughlyfromrust,dust
particles,oilandgrease.
2. Removethesharpcornersandburrsbyfilingorgrindingandpreparetheworkpieces.
3. Theworkpiecesarepositionedontheweldingtablesuchthat,theTshapeisformed.
4. Theelectrodeisfittedintotheelectrodeholderandtheweldingcurrentissettoapropervalue.
5. Thegroundclampisfastenedtotheweldingtable.
6. Wearingtheapron,handgloves,usingthefaceshieldandholdingthepiecesthearcisstruckand
theworkpiecesaretackweldedatboththeends.
7. ThealignmentoftheTjointischeckedandthetackweldedpiecesarereset,ifrequired.
8. WeldingisthencarriedoutthroughoutthelengthoftheTjointasshowninthefigure.
9. Removetheslag,spattersandcleanthejoint.
Result TheTeejointisthusmade,usingthetoolsandequipmentasmentionedabove.
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Chapter4
MACHINESHOP
4.1INTRODUCTION
Inamachineshop,metalsarecuttoshapeondifferentmachinetools.Alatheisusedtocutand
shape themetalby revolving theworkagainstacutting tool.Thework isclampedeither inachuck,
fittedontothelathespindleorinbetweenthecenters.Thecuttingtoolisfixedinatoolpost,mountedonamovablecarriagethat ispositionedonthe lathebed.Thecuttingtoolcanbefedontothework,
either lengthwiseorcrosswise.While turning,thechuckrotates incounterclockwisedirection,when
viewedfromthetailstockend.
4.2PRINCIPALPARTSOFALATHE
Figure4.1showsacenterlathe,indicatingthemainparts.Thenameisduetothefactthatwork
piecesareheldbythecenters.
Figure4.1: Partsofacenterlathe
4.2.1Bed
It is an essential part of a lathe,whichmust be strong and rigid. It carries all parts of themachine and resists the cutting forces. The carriage and the tail stockmove along the guideways
providedonthebed.Itisusuallymadeofcastiron.
4.2.2Headstock
Itcontainseitheraconepulleyorgearingstoprovidethenecessaryrangeofspeedsandfeeds.
Itcontainsthemainspindle,towhichtheworkisheldandrotated.
4.2.3Tailstock
Itisusedtosupporttherighthandendofalongworkpiece.Itmaybeclampedinanyposition
alongthe lathebed.Thetailstockspindlehasan internalMorsetapertoreceivethedeadcenterthat
supportsthework.Drills,reamers,tapsmayalsobefitted intothespindle,forperformingoperations
suchasdrilling,reamingandtapping.
4.2.4CarriageorSaddle
It isused tocontrol themovementof thecutting tool.Thecarriageassemblyconsistsof the
longitudinalslide,crossslideandthecompoundslideandapron.Thecrossslidemovesacrossthelength
ofthebedandperpendiculartotheaxisofthespindle.Thismovementisusedforfacingandtoprovide
thenecessarydepthofcutwhileturning.Theapron,whichisboltedtothesaddle,isonthefrontofthe
latheandcontainsthelongitudinalandcrossslidecontrols.
4.2.5CompoundRest
Itsupportsthetoolpost.Byswivelingthecompoundrestonthecrossslide,shorttapersmaybe
turnedtoanydesiredangles.
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4.2.6ToolPost
Thetoolpost,holdsthetoolholderorthetool,whichmaybeadjustedtoanyworkingposition.
4.2.7LeadScrew
Itisalongthreadedshaft,locatedinfrontofthecarriage,runningfromtheheadstocktothe
tailstock.Itisgearedtothespindleandcontrolsthemovementofthetool,eitherforautomaticfeeding
orforcuttingthreads.
4.2.8Centers
Therearetwocentersknownasdeadcenterand livecenter.Thedeadcenter ispositioned in
thetailstockspindleandthelivecenter,intheheadstockspindle.Whileturningbetweencenters,the
deadcenterdoesnotrevolvewiththeworkwhilethelivecenterrevolveswiththework.
4.3WORKHOLDINGDEVICES
4.3.1Threejawchuck
It is awork holding device having threejaws (selfcentering)whichwill close or openwith
respect to the chuck center or the spindle center, as shown in figure. It is used for holding regular
objectslikeroundbars,hexagonalrods,etc.
Figure4.2: Threejawchuck Figure4.3: Fourjawchuck
4.3.3Faceplate
Itisaplateoflargediameter,usedforturningoperations.Certaintypesofworkthatcannotbe
heldinchucksareheldonthefaceplatewiththehelpofvariousaccessories.
Figure4.4: Faceplate Figure4.5: Lathedoganddrivingplate
4.3.4Lathedogsanddrivingplate
Theseareusedtodriveaworkpiecethatisheldbetweencenters.Theseareprovidedwithan
opening to receive and clamp thework piece and dog tail, the tail of the dog is carried by the pin
providedinthedrivingplatefordrivingtheworkpiece.
4.4MEASURINGINSTRUMENTS
4.4.1OutsideandinsideCalipers
Firmjointorspringcalipersareusedfortransferofdimensionswiththehelpofasteelrule.
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Figure4.6: Calipers
4.4.2VernierCalipers
Verniercaliperisaversatileinstrumentwithwhichbothoutsideandinsidemeasurementsmay
bemadeaccurately.Theseinstrumentsmayhaveprovisionfordepthmeasurementalso.
Figure4.7: VernierCaliper
4.4.3Micrometers
Outsideand insidemicrometersareusedformeasuringcomponentswheregreateraccuracyis
required.
4.5CUTTINGPARAMETERS
4.5.1Cuttingspeed
It is defined as the speed atwhich thematerial is removed and is specified inmeters per
minute.Tidependsupon theworkpiecematerial, feed,depthofcut, typeofoperationandsomany
othercuttingconditions.Itiscalculatedfromtherelation,
Spindlespeed(RPM)=cuttingspeedx1000/(D)
WhereDistheworkpiecediameterinmm.
4.5.2Feed
Itisthedistancetraversedbythetoolalongthebed,duringonerevolutionofthework.Itsvalue
dependsuponthedepthofcutandsurfacefinishoftheworkdesired.
4.5.3DepthofCut
It is the movement of the tip of the cutting tool, from the surface of the work piece and
perpendicular to the latheaxis. Itsvaluedependsupon thenatureofoperation like rough turningor
finishturning.
4.6TOOLMATERIALS
Generalpurposehandcuttingtoolsareusuallymadefromcarbonsteelortoolsteel.Thesingle
point lathecuttingtoolsaremadeofhighspeedsteel(HSS).themainalloying elements in1841HSS
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toolsare18percent tungsten,4percentchromiumand1percentvanadium.5 to10percentcobalt is
alsoaddedtoimprovetheheatresistingpropertiesofthetool.
Carbidetippedtoolsfixedintoolholders,aremostlyusedinproductionshops.
4.7TOOLGEOMETRY
Asinglepointcuttingtoolusedonlathemaybeconsideredasasimplewedge.Figure4.8shows
thecommonturningtoolsusedfordifferentoperations.Figure6.9showsthebasicanglesofasimple
turningtool.
Figure4.8:Commonturningtools Figure4.9:Toolgeometry
4.8LATHEOPERATIONS
4.8.1Turning
Cylindricalshapes,bothexternalandinternal,areproducedbyturningoperation.Turningisthe
processinwhichthematerialisremovedbyatraversingcuttingtool,fromthesurfaceofarotatingwork
piece.Theoperationusedformachininginternalsurfacesisoftencalledtheboringoperationinwhichaholepreviouslydrilledisenlarged.
Forturninglongwork,firstitshouldbefacedandcenterdrilledatoneendandthensupported
bymeansofthetailstockcentre.
4.8.2Boring
Boring isenlargingaholeandisusedwhencorrectsizedrill isnotavailable.However,itshould
benotedthatboringcannotmakeahole.
4.8.3Facing
Facing isamachiningoperation,performedtomaketheendsurfaceoftheworkpiece,flatand
perpendiculartotheaxisofrotation.Forthis,theworkpiecemaybeheldinachuckandrotatedabout
the lathe axis.A facing tool is fedperpendicular to the axisof the lathe.The tool is slightly inclinedtowardstheendoftheworkpiece.
4.8.4TaperTurning
A taper isdefinedas theuniformchange in thediameterofaworkpiece,measuredalong its
length. It is expressed asa ratioof thedifference indiameters to the length. It is alsoexpressed in
degreesofhalftheincluded(taper)angle.
Taperturningreferstotheproductionofaconicalsurface,ontheworkpieceonalathe.
Shortsteeptapersmaybecutona lathebyswivelingthecompoundresttotherequiredangle.Here,thecuttingtoolisfedbymeansofthecompoundslidefeedhandle.Theworkpieceisrotatedinachuck
orfaceplateorbetweencenters.
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4.8.5Drilling
Holesthatareaxiallylocatedincylindricalpartsareproducedbydrillingoperation,usingatwist
drill.For this, theworkpiece is rotated inachuckor faceplate.The tailstockspindlehasastandard
taper.Thedrillbitisfittedintothetailstockspindledirectlyorthroughdrillchuck.Thetailstockisthen
movedoverthebedandclampedonitnearthework.Whenthejobrotates,thedrillbitisfedintothe
workbyturningthetailstockhandwheel.
4.8.6
Knurling
Itistheprocessofembossingadiamondshapedregularpatternonthesurfaceofaworkpiece
usingaspecialknurling tool.This toolconsistsofa setofhardened steel rollers inaholderwith the
teethcutontheirsurfaceinadefinitepattern.Thetoolisheldrigidlyonthetoolpostandtherollersare
pressedagainsttherevolvingworkpiecetosqueezethemetalagainstthemultiplecuttingedges.The
purposeofknurlingistoprovideaneffectivegrippingsurfaceonaworkpiecetopreventitfromslipping
whenoperatedbyhand.
4.8.7Chamfering
Itistheoperationofbevelingtheextremeendofaworkpiece.Chamfer isprovidedforbetter
look,toenablenuttopassfreelyonthreadedworkpiece,toremoveburrsandprotecttheendofthe
workpiecefrombeingdamaged.
4.8.8Threading
Threading isnothingbutcuttinghelicalgrooveonaworkpiece.Threadsmaybecuteitheron
the internalor external cylindrical surfaces.A specially shaped cutting tool, knownas thread cutting
tool,isusedforthispurpose.Threadcutting ina latheisperformedbytraversingthecuttingtoolata
definiterate,inproportiontotherateatwhichtheworkrevolves.
Figure4.10:OperationsofLathe
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4.9SAFETYPRECAUTIONS
1. Alwaysweareyeprotection preferablyindustrialqualitysafetyglasseswithsideshields.Thelathe
canthrowoffsharp,hotmetalchipsatconsiderablespeedaswellasspinoffspiralsofmetalthat
canbequitehazardous.Don'ttakechanceswithyoureyes.
2. Wearshortsleeveshirts,loosesleevescancatchonrotatingworkandquicklypullyourhandorarm
intoharm'sway.
3. Wearshoes
preferably
leather
work
shoes
to
protect
your
feet
from
sharp
metal
chips
on
the
shopfloorandfromtoolsandchunksofmetalthatmaygetdropped.
4. Removewristwatches,necklaces,chainsandotherjewelry.Tiebacklonghairsoitcan'tgetcaught
intherotatingwork.Thinkaboutwhathappenstoyourfaceifyourhairgetsentangled.
5. Alwaysdoublechecktomakesureyourwork issecurelyclamped inthechuckorbetweencenters
beforestartingthelathe.Startthelatheatlowspeedandincreasethespeedgradually.
6. Get in thehabitof removing thechuckkey immediatelyafteruse.Someusers recommendnever
removing yourhand from the chuck keywhen it is in the chuck. The chuck key can be a lethal
projectileifthelatheisstartedwiththechuckkeyinthechuck.
7. Keepyourfingersclearoftherotatingworkandcuttingtools.Thissoundsobvious,butIamoften
temptedtobreakawaymetalspiralsastheyformatthecuttingtool.
8. Avoidreachingoverthespinningchuck.Forfilingoperations,holdthetangendofthefile inyour
lefthand
so
that
your
hand
and
arm
are
not
above
the
spinning
chuck.
9. Neveruseafilewithabaretang thetangcouldbeforcedbackintoyourwristorpalm.
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ME101WorkshopPracticeI Machineshop
Exercise1Facingandplainturning
Aim
Toobtainrequireddiameterofacylindricalworkpiecewiththegivenlength(Fig4.11).Tools&Equipment
Lathemachine.Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,
outsidecalipersorverniercalipers.
Sketch 2x45
28.50.2
1300.2
FigureMSE1: Plain Turning
Theory
Facingistheoperationsoffinishingtheendsofworktomakeendsflat,smoothandtorequiredlength.
Roughturningoperationisusedwhereexcessivestockistoberemovedandsurfacefinishisnotcritical.
Forsuchaoperationdeepcutswithcoarsefeedareused.Duringroughmachining,maximummetal is
removedand
very
little
oversize
dimension
isleft
for
finishing
operation.
Procedure
1. Thegivenworkpieceisheldinthe3jawchuckofthelathemachineandtightenedfirmlywithchuck
key.
2. Righthand singlepointcutting tool is taken tightened firmlywith thehelpofboxkey in the tool
post.
3. Machine isswitchedonandthetoolpost isswiveledandthecuttingpoint isadjustedsuchthat it
positionedapproximatelyforfacingoperationthenthetoolisfedintotheworkpieceandthetool
postisgiventhetransversemovementbyrotatingthehandwheelofthecrossslide.
4. Withthisfacingiscompletedandthetoolpostisswiveledandcuttingpointismadeparalleltothe
axisofworkpiece.
5. Depthofcut isgivenbycrossslidetothetoolpostandthesidehandwheel isrotatedtogivethe
longitudinalmovementforthetoolpostandjobisturnedtotherequiredlengthanddiameter.
6. Aftercompletionofthejob it is inspectedfor thedimensionsobtainedwith thehelpofsteelrule
andoutsidecaliperorverniercaliper.
Precautions
1. Workpieceshouldbeheldfirmly.
2. Inroughturningoperationdonotoverfeedthetool,asitmaydamagethecuttingpointofthetool.
3. Exerciseoverhungof tool shouldbeavoidedas it results in chatterand causes roughmachined
surface.
4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointtotheouterdiameteroftheworkpiece.
Result Thejobisthusmadeaccordingtothegivendimensions.
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ME101WorkshopPracticeI Machineshop
Exercise2Stepturning
Aim
Toobtainrequireddiameters(steps)onacylindricalworkpiecewiththegivenlengths.Tools&Equipment
Lathemachine.Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,
outsidecalipersorverniercalipers.
Theory
Step turning is the operation of creating various cylindrical cross sections on ametal blank. Rough
turningoperation isusedwhereexcessivestock istoberemovedandsurfacefinish isnotcritical.For
such a operation deep cutswith coarse feed are used. During roughmachiningmaximummetal is
removedandverylittleoversizedimensionisleftforfinishingoperation.
Sketch
2x45
2616 16 22 26
40 33 27
FigureMSE2: StepTurning
Procedure
1. The givenwork piece is held in the 3jawchuckof the lathemachine and tightened firmlywith
chuckkey.
2. Righthandsinglepointcutting tool istakentightened firmlywith thehelpofboxkey in thetool
post.
3. Machineisswitchedonandthetoolpostisswiveledandthecuttingpointisadjustedsuchthatit
positionedapproximatelyforfacingoperationthenthetoolisfedintotheworkpieceandthetool
postisgiventhetransversemovementbyrotatingthehandwheelofthecrossslide.
4. Withthisfacingiscompletedandthetoolpostisswiveledandcuttingpointismadeparalleltothe
axisofworkpiece.
5. Depthofcutisgivenbycrossslidetothetoolpostandthesidehandwheelisrotatedtogivethe
longitudinalmovement for the toolpostandjob is turned to the required lengthanddiameters
accordingtothesketchshowninfigure.6. Aftercompletionofthejobit is inspectedforthedimensionsobtainedwiththehelpofsteelrule
andoutsidecaliperorverniercaliper.
Precautions
1. Workpieceshouldbeheldfirmly.
2. In rough turningoperationdonotover feed the tool,as itmaydamage thecuttingpointof the
tool.
3. Exerciseoverhungof toolshouldbeavoidedas it results inchatterandcauses roughmachined
surface.
4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointto
theouterdiameteroftheworkpiece.
Result Thejobisthusmadeaccordingtothegivendimensions.
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ME101WorkshopPracticeI Machineshop
Exercise3Shoulder turning
Aim
Toobtainrequireddiametersonacylindricalworkpiecewiththegivendimensions.Tools&Equipment
Lathemachine,Mildsteelbar,righthandcuttingtool,boxkeyor toolpostkey,chuckkey,steelrule,
outsidecalipersorverniercalipers.
Sketch
Figure4.13: ShoulderTurning
Procedure
1. Thegivenworkpieceisheldinthe3jawchuckofthelathemachineandtightenedfirmlywithchuck
key.
2. Righthand singlepointcutting tool is taken tightened firmlywith thehelpofboxkey in the tool
post.3. Machine isswitchedonandthetoolpost isswiveledandthecuttingpoint isadjustedsuchthat it
positionedapproximatelyforfacingoperationthenthetoolisfedintotheworkpieceandthetool
postisgiventhetransversemovementbyrotatingthehandwheelofthecrossslide.
4. Withthisfacingiscompletedandthetoolpostisswiveledandcuttingpointismadeparalleltothe
axisofworkpiece.
5. Depthofcut isgivenbycrossslidetothetoolpostandthesidehandwheel isrotatedtogivethe
longitudinalmovementforthetoolpostandjobisturnedtotherequiredlengthanddiameters.
6. Aftercompletionofthejob it is inspected for thedimensionsobtainedwith thehelpofsteelrule
andoutsidecaliperorverniercaliper.
Precautions
1. Workpieceshouldbeheldfirmly.
2. Inroughturningoperationdonotoverfeedthetool,asitmaydamagethecuttingpointofthetool.3. Exerciseoverhungof tool shouldbeavoidedas it results in chatterand causes roughmachined
surface.
4. Itisimportanttoensurethatduringfacingoperationthecuttingisperformedfromcenterpointto
theouterdiameteroftheworkpiece.
Result Thejobisthusmadeaccordingtothegivendimensions.
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References
WorkshopmanualbyP.Kannaiah&K.L.Narayana
www.technologystudent.com
www.wikipedia.orgwww.mewelding.com