Introduction to Lathe Machine Reference: Elements of Workshop Technology (Vol. 2) Hajra Choudhary and web ref.

1. - By Virag A. Timbadia
Lecturer – SBM Polytechnic

2. Introduction
• Definition:
Lathe is a machine, which removes the metal from a work piece to the
required shape & size
• Principle:
A lathe operates on the principle of a rotating work piece and a fixed
cutting tool. The cutting tool is feed into the work piece, which rotates
about its own Z-axis, causing the work piece to be formed to the desired
shape.
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3. Lathe MachineComponents
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4. ViragA.Timbadia
LatheMachineComponents
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5. Lathe MachineComponents
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6. ViragA.Timbadia
Lathe MachineComponents
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7. Classification
Lathe
Machine
Speed lathes
Engine lathes
Bench lathes
Capstan and turret lathes
Automatic lathes
Computer controlled lathes
Tracer lathes
Tool Room lathes
Special Purpose lathes
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Wood working
Polishing
Spinning
Belt drive
Gear head lathe
Missile Lathe
Gap Bed Lathe
T-Lathe
Wheel Lathe
Duplicating Lathe
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8. • Speed lathes: High speed lathe with very few ranges of speed and use for
wood working, centering polishing and spinning.
• Engine lathes: This is similar to the speed lathes but the head stock is little
robust in construction. Engine lathes have additional mechanisms to
produce a wide range of speeds.
• Bench lathes: This is a very small lathe and is generally mounted over a
bench. These lathes are small in size and are generally used for doing small
and precision works.
• Capstan and turret lathes: These are the developments made in engine
lathe. These lathes found application in production work. In this lathes the
tail stock is replaced by hexagonal turret. Based on the way the turret is
mounted they will be classified in to capstan and turret lathes.
• Automatic lathes: Every operation is automatically done by employing
computers. These lathes have high speed, heavy duty and are used for mass
production. These lathes produce jobs with minimum tolerances and of very
high accuracy.
• Tracer lathes: a lathe that has the ability to follow a template to copy a
shape or contour.
• Tool Room lathes: it is more accurately built and a wide range of speeds
ranging from very low to very high speeds up to 2500rpm can be generated.
This is used for doing precision works like tools dies etc. tool room lathes
are costlier when compared to engine lathes of same size.
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9. Specification
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1. The length of bed :
It indicates the approximate floor space occupied by the lathe.
2. The length between centers :
It is the maximum length of work that can be mounted between the lathe
centers.
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BED
SWING DIAMETER OVER BED
HEIGHT OF CENTRE FROM BED
SWING DIAMETER OVER CARRIAGE
CARRIAGE
Specification
3. The height of centers from the bed : It is the distance between top surface of the bed
and the imaginary center line passing through live centre and dead centre.
4. The maximum bar diameter : It is the maximum diameter of work that will pass
through the hole of the head stock spindle.
5. The swing diameter of work over bed : It is the largest diameter of work that will
revolve without touching the bed. It is twice the height of the centres from the bed.
6. The swing diameter of work over the carriage : It is the largest diameter of work that
will revolve over the lathe saddle. It is smaller than the swing diameter over bed.
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11. ViragA.Timbadia
Lathe Tools
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12. Components
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Lathe Bed &
Ways
Head Stock Speed Gears Feed Gears Thread Chasing Dial
(1/2 Nut)
Carriage Cross Slide Compound Tail Stock Coolant System
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13. BED
The bed of the lathe provides
the foundation for the entire
machine and holds various
components like headstock,
tailstock and carriage in
alignment.
Components
WAY
The surfaces of the bed that are
finely machined - and upon which
the carriage and tailstock slide - are
known as "ways".
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14. Components
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HEADSTOCK
The headstock of the lathe
contains all of the gearing
necessary to change
• Spindle speed
• Carriage feed and
• Threading selections.
SPEED & FEED GEARS
The lathe “speed” and
“feed” charts are affixed to
the front of the headstock to
allow the operator to make
the proper feed and speed
selections based on the
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15. Components
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CARRIAGE ASSEMBLY
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16. Components
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CARRIAGE OPERATING CONTROL
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17. Magnetic Tool Post
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Lead & Feed Screw
Single Tool Tool-Post
Apron Msm.
Components
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18. Components
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19. Components
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20. Lathe Accessories
• Divided into two categories
– Work-holding, - Supporting, & - Driving Devices
• Lathe centers, chucks, faceplates
• Mandrels, steady and follower rests
• Lathe dogs, drive plates
– Cutting-tool-holding devices
• Straight and offset tool holders
• Threading tool holders, boring bars
• Turret-type tool posts
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21. •Work to be turned between
centers must have center hole
drilled in each end
– Provides bearing surface
•Support during cutting
•Most common have solid
Morse taper shank 60º centers,
steel with carbide tips
•Care to adjust and lubricate
occasionally
Lathe Centers
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22. Removing & Mounting
Lathe Centers
• Live center
– Use knockout bar pushed through headstock spindle (slight tap)
• Use cloth over center and hold to prevent damage
• Dead center
– Turn tailstock hand wheel to draw spindle back into tailstock
• End of screw contacts end of dead center, forcing it out of spindle
• Remove any burrs from lathe spindle, centers, or spindle sleeves
• Clean tapers on lathe centers and in headstock and tailstock spindles
• Partially insert cleaned center in lathe spindle
– Force center into spindle
• Follow same procedure when mounting tailstock center
• Check trueness of center
– Use dial indicator
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23. RevolvingTailstockCenters
• Replaced solid dead centers for most machining operations
• Used to support work held in chuck or when work is being machined
between centers
• Contains antifriction bearings which allow center to revolve with work piece
– No lubrication required between center and work
• Types: revolving dead center, long point center, and changeable point center
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24. MicrosetAdjustableCenter
• Fits into tailstock spindle
• Provides means of aligning lathe centers or producing slight tapers on work
machined between centers
• Eccentric slide (dovetail) allows center to be adjusted limited amount to
each side of center
Self-DrivingLive Center
• Mounted in headstock spindle
• Used when entire length of work piece is being machined in one operation
– Chuck or lathe dog could not be used to drive work
• Grooves ground around circumference of lathe center point provide drive
• Work usually soft material such as aluminum
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25. Chucks
• Used extensively for holding work for lathe machining operations
– Work large or unusual shape
• Most commonly used lathe chucks
– Three-jaw universal
– Four-jaw independent
– Collets chuck
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26. Three-jawUniversalChuck
• Holds round and hexagonal work
• Grasps work quickly and accurate within few thousandths/inch
• Three jaws move simultaneously when
adjusted by chuck wrench
– Caused by scroll plate into which all three jaws fit
• Two sets of jaw: outside chucking and inside chucking
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27. Four-Jaw Independent Chuck
• Used to hold round, square, hexagonal, and irregularly shaped work pieces
• Has four jaws
– Each can be adjusted independently by chuck wrench
• Jaws can be reversed to hold work by inside diameter
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28. ColletChucks
• Most accurate chuck
• Used for high-precision work
• Spring collets available to hold round, square, or hexagon-shaped work
pieces
• Each collet has range of only few thousandths of an inch over or under size
stamped on collet
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29. SpringColletChucks
• Spring - collet chuck
– One form: Hand wheel draws collet into tapered adapter
– Another form: Uses chuck wrench to tighten collet on work piece
• Can hold larger work than draw-in type
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30. JacobsColletChuck
• Jacobs collet chuck
– Utilizes impact-tightening hand wheel to close collets
– Wider range than spring-collet chuck
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31. MagneticChucks
• Used to hold iron or steel parts that are too thin or may be damaged if held
in conventional chuck
• Fitted to an adapter mounted on headstock spindle
• Used only for light cuts and for special grinding applications
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32. HeadstockSpindleTypes
1. Threaded
spindle nose:
Screws on in
C.W. direction
3. Tapered
spindle Nose:
Held by lock nut
that tightens on
chuck
2. Cam-lock spindle nose:
Held by tightening cam-locks using T-wrench
Chuck aligned by taper on spindle nose
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33. Faceplates
• Used to hold work too large or shaped so it cannot be held in chuck or
between centers
• Usually equipped with several slots to permit use of bolts to secure work
– Angle plate used so axis of work piece may be aligned with lathe
centers
• Counterbalance fastened to faceplate when work mounted off center
– Prevent imbalance and resultant vibrations
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34. Steady rest
• Used to support long work held
in chuck or between lathe centers
– Prevent springing
• Located on and aligned by ways
of the lathe
• Positioned at any point along
lathe bed
• Three jaws tipped with plastic,
bronze or rollers may be adjusted
to support any work diameter
with steady rest capacity
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35. FollowerRest
• Mounted on saddle
• Travels with carriage to prevent
work from springing up and
away from cutting tool
– Cutting tool generally
positioned just ahead of
follower rest
– Provide smooth bearing
surface for two jaws of
follower rest
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36. Mandrel
• Holds internally machined work piece between centers so further
machining operations are concentric with bore
Plain Mandrel
Stub Mandrel
Gang Mandrel
Expanding Mandrel
• Several types, but most
common are:
-Plain Mandrel
-Expanding Mandrel
-Stub Mandrel
-Gang Mandrel
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37. LatheDogs
• Drives work machined between centers
• Has opening to receive work and setscrew to fasten the dog to work
• Tail of dog fits into slot on drive plate and provides drive to work piece
• Made in variety of sizes and types to suit various work pieces
 Standard bent-tail lathe dog:
• Most commonly used for round work pieces
• Available with square-head setscrews of headless setscrews
• Bent tail engages in slot on drive plate
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38.  Straight-tail lathe
dog
• Driven by stud in
drive plate
• Used in precision
turning
 Safety Clamp
lathe dog
• Used to hold variety
of work
• Wide range of
adjustment
 Heavy Duty lathe
dog
• Wider Range than
others
• Used on all shapes
LatheDogs
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39. Cutting Tool-Holding Devices
• Available in three styles
– Left-hand offset
– Right-hand offset
– Straight
• Each has square hole to accommodate square tool-bit held in place by
setscrew
– Angle of approximately 15º to 30º to base of tool-holder
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40.  LH Offset tool holder
• Offset to the right
• Designed for machining work close
to chuck or faceplate and cutting
right to left
• Designated by letter L
RH Offset tool holder
• Offset to the left
• Designed for machining work close
to the tailstock and cutting left to
right
• Designated by letter R
Offset Tool holder
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41. Toolholder
 Straight Tool Holder
• General-purpose type
• Used for taking cuts in either direction
and for general machining operations
• Designated by letter S
 Carbide Tool Holder
• Has square hole parallel to base of
tool holder to accommodate carbide-
tipped tool bits
• Holds tool bit with little or no back
rake
• Designated by letter C
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42. Cutting-Off (Parting)Tools
• Used when work must be grooved or parted off
• Long, thin cutting-off blade locked securely in tool holder by either cam
lock or locking nut
• Three types of parting tool holders
– Left-hand
– Right-hand
– Straight
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43. ThreadingToolholder
• Designed to hold special form-relieved thread-cutting tool
• Has accurately ground 60º angle
– Maintained throughout life of tool
– Only top of cutting surface sharpened when becomes dull
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44. Boring Toolholders
• Held in standard tool post
– Light boring tool holder
• Used for small holes and light cuts
– Medium boring tool holder
• Suitable for heavier cuts
• May be held at 45º or 90º to axis of bar
• Mounted on compound rest of lathe
– Heavy-duty boring bar holder
• Three bars of different diameters
• May be held at 45º or 90º to axis of bar
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45. CompoundRest ToolingSystems
• Standard, or round, tool post
– Generally supplied with conventional engine lathe
– Fits into T-slot of compound rest
– Provides means of holding and adjusting type of tool holder or cutting
tool required
– Concave ring and the wedge or rocker provide for adjustment of cutting-
tool height
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46. ConventionalToolPosts
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47. Modular(Quick-Change)Tooling
• Initially developed for CNC machine tools
to improve accuracy, reduce tool-change
time and increase productivity
– Benefits realized on conventional lathes
with systems designed for these
machines
• Modular tooling system must be rigid,
accurate and have quick-change capabilities
– Basic clamping unit or turret can hold
variety of cutting tool modules
• Principal function is to reduce cost of
keeping large tool inventory
• Tools can be specifically mounted to suit
characteristics of work piece
• More common systems available
– The Super Quick-Change Tool post
– The Quadra* Index Tool post
– The Super-Six Index Turret
– The Vertical Index Turret
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48. SuperQuick-Change Toolpost
• Provides fast, accurate, and reliable method of quickly changing and setting
various tool holders for different operations
• Locking system has two sliding gibs forced out against tool holder
– Handle pulled into lock position
– Provides rigid, positive lock with zero backlash
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49. Quadra*IndexToolpost
• Allows four tools to be mounted on turret at same time
– Each tool locked independently
– Provides flexibility to use from one to four tools simultaneously
• Unique indexing system of turret allows it to be set in 24 positions (every 15º)
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50. Super-SixIndex Turret
• Designed to simplify and increase machining productivity on engine lathes
when multi-operation jobs require use of more than one tool
– Up to six tools for external and internal machining operations
– Allows height adjustment for each tool
• Tool changes can be made in less than 1 sec
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51. VerticalIndex Turret(VIT)
• Designed to give highest
accuracy, fastest tool change and
greatest rigidity of any tool
system available for engine lathes
• Same concept as indexing turrets
on CNC lathes
– Can hold up to six or eight
tools
– Closest to performance of
CNC lathes
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52. Alignment Test
 Lathe Centers
• When lathe center aligned Parallel diameters produced
• Three common methods used to align
– Aligning tailstock
– Trial Cut
– Test Bar and Indicator
 Leveling of the Machine
 True Running of Work Piece
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53. • Aligning centerlines on back of tailstock with each other
• Only a visual check and not too accurate
1. Loosen tailstock clamp nut or level
2. Loosen one of the adjusting screws, depending on direction tailstock must be
moved and tighten other until line on top aligns with line on bottom half
3. Tighten screw to lock both halves in place
4. Make sure tailstock lines still aligned
5. Lock tailstock clamp nut or lever
Aligning TailStock
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54. 8. If both diameters not same size, adjust
tailstock either toward or away from
cutting tool ½ difference of two
readings
9. Take another light cut at both points at
same cross feed graduated collar setting
10.Measure diameters and repeat.
Trial-CutMethod
• Small cut taken from each end of work
• Diameters measured with a micrometer
1. Take a light cut (.005-.010 in.) to true diameter from section at tailstock end
about .250 in. long
2. Stop feed and note reading on graduated collar of cross feed handle
3. Move cutting tool away from work with cross feed handle
4. Bring cutting tool close to headstock end
5. Return cutting tool to same graduated collar setting as at first cut
6. Cut a .500-in (13 mm) length at headstock end and stop lathe
7. Measure both diameters with micrometer
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55. Test bar anddial indicator
1.Clean lathe and work center, mount test bar
2.Adjust test bar snugly between centers and tighten tailstock spindle clamp
3.Mount dial indicator on tool post or lathe carriage : Indicator plunger should be
parallel to lathe bed and contact point set on center
4.Adjust cross-slide : Indicator registers approximately .025 in at tailstock,
indicator bezel to 0
5.Move carriage by hand so indicator registers on diameter at headstock end and
note indicator reading
6.If both indicator readings not same, adjust tailstock with adjusting screws until
indicator registers same at both ends
7.Tighten adjusting screw & tail stock clamp nut that was loosened
8.Adjust tailstock spindle until test bar snug between lathe centers
9.Recheck indicator readings at both ends and, if necessary, adjust tailstock
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ThreeImportantElements
Rotating Speed
It expresses with the number of rotations (rpm) of the chuck of a lathe. When
the rotating speed is high, processing speed becomes quick, and a processing
surface is finely finished. It is better to set low rotating speed at the first stage.
Cutting Depth
The cutting depth of the tool affects to the processing speed and the roughness
of surface. When the cutting depth is big, the processing speed becomes quick,
but the surface temperature becomes high, and it has rough surface.
Feed (Sending Speed )
The sending speed of the tool also affects to the processing speed and the
roughness of surface. When the sending speed is high, the processing speed
becomes quick. When the sending speed is low, the surface is finished beautiful.

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Mechanisms
1. Cam Slot
2. Guide or Frame
3. Lead Screw
4. Hand Lever
5. Pin
6. Circular Plate
7. Half Nuts
HalfNut Mechanism

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Lathe Operations

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Turning

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Straight Turning

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TaperTurning
Methods of Taper Turning
1. By a broad nose form tool
2. By setting over the tailstock center
3. By swiveling the compound rest
4. By taper turning attachment
5. By Combining longitudinal and cross
feed in a special lathe
1.
3.2.
Set Over = L x
(D−d)
2L
=
(D−d)
L

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TaperTurning
4. 5.

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Facing

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Drilling

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Boring

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Tapping

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Threading

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Knurling

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Reaming

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RadiusForming

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Grooving

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Parting

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Eccentric

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Filing & Polishing

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Filing & Polishing

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