UNIT II Center Lathe

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TURNINGMACHINES

UNIT II


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Introduction

Lathe is a machine, which removes the metal from a piece of work to the

required shape & size

Lathe is the oldest machine tool and came to existence from the early tree

lathe

Lathe was the first machine which came for metal cutting

Large number modern machine tools are found still the lathe machines

are used in modern tool rooms, repair shops and training workshops


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Working principle

Which holds the work piece securely between the two rigid and

strong supports

Tool is rigidly held and supported in a tool post and it is fed against

the revolving work piece

While the work piece revolves about its own axis tool is made to

move in parallel or at an angle with the axis of a material to be cut


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Types of lathe

ench lathe!"mall usually mounted on a bench! #ccurate, precision

"peed lathe!"implest lathe!$% to '( rpm!)o *ear box,+arriage,Lead

screw

ngine lathe!"team engines!-obust

Tool room lathe!Low speed to %. rpm

+apstan and turret lathe!/ass 0roduction #utomatic lathe!1eavy duty!1igh "peed!/ass 0roduction!2uality and

quantity of production

"pecial 0urpose lathe


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A basic manual centrelathe

The lathe is controlled by a

person turning handles

on the top slide and cross

slide in order to make a

part3


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Specifcation o lathe

1eight of the centres

Length between centres

Length of bed

"wing diameter over bed"wing diameter over carriage

/aximum bar diameter

"pindle speed

Lead screw pitch

/otor horse power and -303/


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Setting the tool height

The cutting tool on the lathe

must be set to the exact

centre of the work!piece We use the centre of the

tailstock to guide us to the

correct height


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WORK HOLDING DEVICES

+14+5

4sed extensively for holding work for machining operations

Work large or unusual shape

/ost commonly used lathe chucks

Three!6aw universal

7our!6aw independent

+ollet chuck

/agnetic +huck


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Three-jaw univera!

1olds round and hexagonal work

*rasps work quickly and accurate

Three 6aws move simultaneously when

ad6usted by chuck key

+aused by scroll plate into which all three 6aws fit

Two sets of 6aw8 outside chucking and inside chucking


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"our-jaw inde#endent

4sed to hold round, square, hexagonal, and irregularly shaped work

pieces

1as four 6aws

ach can be ad6usted independently by chuck wrench

9aws can be reversed to hold work

by inside diameter


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Co!!et Chuc$

:

"pecial adapter fitted into taper

of headstock spindle, and hollow

draw bar having internal threadinserted in opposite end of

headstock spindle3

;t draws collet into tapered

adapter causing collet to tighten on

work piece


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Magnetic Chuck

Thin 6obs can be held by means ofThin 6obs can be held by means of

magnetic chucks3magnetic chucks3


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"ace #!ate

# lathe faceplate is a basic work

holding accessory for a wood or metal

turning lathe3 ;t is a circular metal


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Do%

;t is a device that clamps around the work piece and allows the rotary

motion of the machine>s spindle to be transmitted to the work piece


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&andre!

an ob6ect used to shape machined, or

electroformed, work3

a tool component that grips or clamps

materials to be machined3

a tool component that can be used to

grip other moving tool components3


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Rests


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Lathe 'ed

/ade from rigid cast ;ron

#ccurately machined slide ways

"lide ways guide carriage &

tailstock

1eadstock on upper end of the

lathe bed

Contd


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Contd...

Headtoc$

1olds lathe spindle and gears

+huck is fitted to spindle

"pindle is hollow for long bars


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Contd...

Tai!toc$

+an be moved along slide

ways

+an be clamped

in any location

;nside tapered

to hold drill chuck


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Contd...

Carria%e

/oves along bed between

tailstock and headstock

"addle ? across the lathe

#pron ? hangs down in front


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Contd...

Cro S!ide

7itted on the "addle

/oves cutting tool at right

angles to lathe bed


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Contd...

Co(#ound !ide

7itted to top of +ross slide

+arries tool post and cutting

tool

+an rotate to any angle

;s used to turn tapers


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Contd...

"eed ha)t

4sed to move the +arriage

automatically

Lead crew

4sed when screw cutting

on the lathe


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Lathe parts

Too! *ot

7itted on top slide and carries the

cutting tool or the cutting tool

holder

+an ad6ust the height on some

types

+an carry @ different tool holders


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Lathe parts

Too! ho!der

4sed for holding cutting

tool bits

#vailable in -ight hand,

left hand and straight


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Lathe operations

Faing

-educing the length of work piece

The tool is moved at right angles

to the work using the cross slide

7lat surfaces are produced


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Parallel urning

The tool moved parallel tothe work and cylindricalshapes are

formed

#lso known as sliding


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!nurling

A !n"rling tool is "sed to press apattern onto a ro"nd setion.

The pattern is nor#ally "sed as a gripfor a handle.This pro$ide a grip for the ro"nd part

e.g. Sre%dri$er


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!nurling Shapes


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Parting o"

If %ant to "t o& thepart they ha$e t"rned'they an "se theha!sa% and a $ie or"se the parting o&tool on the lathe.


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Conto"r T"rning

;nstead of feeding the tool

parallel to the axis of

rotation, tool follows a

contour that is notnecessarily straight


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Cha#fering

+utting edge cuts an angle on

the corner of the cylinder,

forming a AchamferA


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hreading

0ointed form tool is fed

linearly across surface of

rotating work part parallel to

axis of rotation at a large feed

rate, thus creating threads


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Taper T"rning

# large variety of articles ,used in engineering practice are found to

have conical shape or flat

+omponents having a gradual reduction in its width or thickness

along their length

# uniform increase or decrease in diameter of work piece


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Contd(


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aper urning Methods

# taper may be turned on the lathe by feeding the tool at an angle to the

rotation axis of the work piece

;t is essential that the cutting edge of the tool should be set accurately on

the centre line of the work piece

There are various methods turning taper on a work piece

4sing tailstock set over method

y swivelling the compound rest

4sing taper turning attachment

4sing form or broad tool


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+SING T,ILSTOCK SET OVER &ETHOD

B ! dover, " C tan

%

, B C igger diameter

d C "maller diameter

of the work piece

LCBistance between live center to dead center3

Set L Ll

Where

l Length

=

=

tanD d

=


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. SWIVELLING THE CO&*O+ND RESTtan

%

, B C igger diameter

d C "maller diameter

C Length of the work piece

l

Where

l

=


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+SING T,*ER T+RNING ,TT,CH&ENT


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T,*ER T+RNING . +SING "OR& TOOL &ETHOD


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/#+1;);)* T;/ #)B 0DW- "T;/#T;D)

Turning Time

9ob lengthLj mm

7eedf mmErev

9ob speedNrpm

fN mmEmin

tC L9 E

Documents

UNIT II Center Lathe