The document provides information about different types of lathe machines and their components and operations. It describes the basic components of lathes like the bed, headstock, tailstock, apron, carriage, and leadscrew. It explains that lathes operate by rotating the workpiece against a cutting tool that can be moved and positioned precisely. Different types of lathes are discussed, including engine lathes, turret lathes, CNC lathes, and automatic lathes. Common turning operations like turning, facing, boring, and threading are also summarized.

1. LATHE MACHINE
PROCESSES & OPERATIONS

2. Introduction
 The lathe operates on the principle of the
work being rotated against the edge of a
cutting tool.
 It is one of the oldest and most important
machine tools.
 The cutting tool is controllable and can be
moved lengthwise on the lathe bed and into
any desired angle across the revolving work.

3. Types of Lathes
 Speed
 Simple construction of a head stock and tail stock
with a tool post. Used for wood turning, metal
polishing, or metal spinning.
 Engine
 Most frequently used lathe
 Heavy duty
 power drive for most tool movements
 Size range 12”x24” to 24”x48” - can be larger

4. Types of Lathes (contd.)
 CNC
 Computer controlled
 Wide variety of process capability
 multiple axis
 Indexing and contouring head
 On- line and off- line programming available

5. CNC Lathe & Turret

6. Types of Lathes (contd.)
 Toolroom
 Greater accuracy
 More versatility
 Wider range of speeds and feeds
 Capstan & Turret
 Hex turret replaces tailstock
 Multiple tools set to machine part
 High production rates
 Still may require some operator skill

7. Turret Lathe
 Capable of performing multiple cutting operations on the same
workpiece
 Turning
 Boring
 Drilling
 Thread cutting
 Facing
 Turret lathes are very versatile
 Types of turret lathes
 Ram-type: ram slides in a separate base on the saddle
 Saddle type:
 more heavily constructed
 Used to machine large workpeiceces

8. Turret Lathe

10. Difference between Capstan & Turret Lathe
Turret Lathe
Capstan Lathe

12. Types of Lathes (contd.)
Tracer Lathes
 Machine tools with attachments
 Capable of turning parts with various contours
 A tracer finger follows the template and guides the cutting tool
Automatic Lathes
 Automatic cutting off lathe
 Single spindle automatic lathe
 Swiss type automatic lathe, screw machines multiple spindle
automatic lathes

13. Types of Lathes (contd.)
Automatic Bar Machines
 Formerly called automatic screw machines
 Designed for high-production-rate machining of screws and other
threaded parts
 All operations are preformed automatically
 Equipped with single or multiple spindles

14. Types of Lathes (contd.)
1
2
3

15. Lathe Size
 Lathe size is determined by the SWING and LENGTH OF THE BED.
The swing indicates the largest diameter that can be turned over the
ways (flat or V-shaped bearing surface that aligns and guides movable
part of machine). Bed length is entire length of the ways.
 Bed length must not be mistaken for the maximum length of the work
that can be turned between centers. The longest piece that can be
turned is equal to the length of the bed MINUS the distance taken up
by the headstock and tailstock.
 As an example, consider the capacity and clearance of a modern 13 in
by 6 ft (325mm by 1800mm) lathe:
Swing over bed 13 in (325mm)
Swing over cross slide 8 3/4 in. (218mm)
Bed length 72 in. (1800mm)
Distance between centers 50 in. (1240mm)

16. Various Cutting Operations
 Turing – produces straight, conical, curved, or grooved
workpieces
 Facing – produces a flat surface at the end of the part
 Boring – to enlarge a hole
 Drilling - to produce a hole
 Cutting off – to cut off a workpeiece
 Threading – to produce threads
 Knurling – produces a regularly shaped roughness

17. Lathe Operations

18. Turning Operations
Schematic illustration of the basic turning operation, showing depth-of-cut, d; feed, f; and
spindle rotational speed, N in rev/min. Cutting speed is the surface speed of the
workpiece at the tool tip.

19. Summary of
Turning
Parameters
and
Formulas

20. Forces Acting on a Cutting Tool in Turning
Forces acting on a cutting tool in turning, Fc is the cutting force, Ft is the thrust of feed force (in the
direction of feed), and Fr is the radial force that tends to push the tool away from the workpiece
being machined.

21. Basic Turning Operations

22. Knurling

23. Standard Engine Lathe
Schematic of a standard engine lathe performing a turning operation, with the cutting tool shown in inset.

24. Engine Lathe Parts

25. Engine Lathe Parts

26. Lathe Design and Terminology
 Lathe Engine essential
components:
 Bed
 Gray cast for vibration
dampening
 Headstock assembly
 Spindle
 Transmission
 Drive motor
 Tailstock assembly
 Longitudinal way clamp
 Transverse way clamp
 Quill for cutting tools,
live centers, or dead
centers
Schematic diagram of an engine lathe, showing basic components.

27. Lathe Design and Terminology
 Lathe Engine essential
components:
 Quick-change gearbox
 Powers Carriage
Assembly movement
with lead screw
 Carriage Assembly
 Fixed to cross slide
 Holds tool post at
variable orientations
 Provides longitudinal
and transverse
movement of tooling
 Ways
 Provides precise
guidance to carriage
assembly and
tailstock
Schematic diagram of an engine lathe, showing basic components.

28. Lathe Design and Terminology

29. Lathe Design and Terminology

30. Lathe Design and Terminology

31. Lathe Components

32. Lathe Components

33. Lathe Components

34. Lathe Components
 BED
The bed of the lathe provides the foundation for the whole machine and holds
the headstock, tailstock and carriage in alignment. The surfaces of the bed
that are finely machined - and upon which the carriage and tailstock slide -
are known as "ways".
Some beds have a gap near the headstock to allow extra-large diameters to
be turned. Sometimes the gap is formed by the machined ways stopping
short of the headstock, sometimes by a piece of bed that can be unbolted,
removed and lost.
Some very large lathes have a "sliding bed" where the upper part, on which
the carriage and tailstock sit, can be slid along a lower separate part - and so
make the gap correspondingly larger or smaller.
 SADDLE
The casting that fits onto the top of the bed and slides along it is known,
almost universally, as the "Saddle" - a self-explanatory and very suitable
term.

35. Lathe Components
APRON
 The vertical, often flat and rectangular "plate" fastened to the front of the
"Saddle" is known as the "Apron" and carries a selection of gears and
controls that allow the carriage to be power driven up and down the bed -
and also engage the screwcutting feed and various powered tool feeds,
should they be fitted. The leadscrew, and sometimes a power shaft, usually
pass through the apron and provide it with a drive for the various functions it
has to perform.
 Apron design can be roughly divided into "single-wall" and "double-wall"
types. The "single-wall" apron has just one thickness of metal and,
protruding from it (and unsupported on their outer ends) are studs that carry
gears. The "double-wall" apron is a much more robust structure, rather like a
narrow, open-topped box with the gear-carrying studs fitted between the two
walls - and hence rigidly supported at both ends

36. Lathe Components
CROSS SLIDE and TOP SLIDE
 Sitting on top of the "Saddle" is the "Cross Slide" - that, as its name implies,
moves across the bed - and on top of that there is often a "Top Slide" or
"Tool Slide" that is invariably arranged so that it can be swiveled and locked
into a new position.
 Very early lathes had a simple T-shaped piece of metal against which the
turner "rested" his tool (all turning being done by hand) but when it became
possible to move this "Rest" across the bed by a screw feed it became
known, appropriately enough, as a "Slide-rest".
 When two slides are provided (or sometimes, on watchmaker's lathes, three)
the complete assembly is known as a "Compound" or "Compound Slide" or
even "Compound Slide-rest". Some makers label the "Top Slide" as the
"Compound Rest" or even the "Compound Slide" - but as "to compound"
means the 'joining of two or more' - not 'one' - so this is not a correct use of
the term.

37. Lathe Components
 CARRIAGE
The whole assembly of Saddle, Apron, Top and Cross Slide is known as the
"Carriage". Some American publications (even makers' handbooks) have
been known to casually refer to the "Saddle" as the "Carriage" - but this
incorrect.
 HEADSTOCK.
The lathe Headstock used, at one time, to be called the "Fixed Headstock" or
"Fixed Head", and the rotating shaft within it the "Mandrel". Today the mandrel
is usually called the "Spindle", but this can cause confusion with the tailstock,
where the sliding bar is known variously as the "ram", "barrel" - and "spindle".
The headstock is normally mounted rigidly to the bed (exceptions exist in
some production and CNC lathes) and holds all the mechanisms, including
various kinds and combinations of pulleys or gears, so that the spindle can be
made to turn at different speeds.

38. Lathe Components
 HEADSTOCK SPINDLE
The end of the headstock spindle is usually machined so that it can carry a
faceplate, chuck, drive-plate, internal or external collets - or even special
attachments designed for particular jobs. In turn, these attachments hold the
workpiece that is going to be machined.
 BACKGEAR
As its name implies, "backgear" is a gear mounted at the back of the
headstock (although in practice it is often located in other positions) that
allows the chuck to rotate slowly with greatly-increased torque (turning
power).

39. Lathe Components
 LEADSCREW
Originally termed a "master thread", or described as the "leading screw", but now
always referred to as the "leadscrew", this is a long threaded rod normally found
running along the front of the bed or, on some early examples running between
the bed ways down the bed's centre line. By using a train of gears to connect the
lathe spindle to the leadscrew - and the leadscrew to the lathe carriage - the
latter, together with its cutting tool, could be forced to move a set distance for
every revolution of the spindle.
 TAILSTOCK
The Tailstock was once known as the "Loose headstock", " Poppet head" or
"Loose head“. The unit is arranged to slide along the bed and can be locked to it
at any convenient point; the upper portion of the unit is fitted with what is variously
called a "barrel", "spindle" "ram" or "shoot" that can be moved in and out of the
main casting by hand, lever or screw feed and carries a "Dead Centre" that
supports the other end of work held (by various means) in the headstock.
Special centres, which rotate with the work, can be used in the tailstock ; these
are known as "Rotating Centres" and should not be referred to as "live centres" -
that term being reserved for the centre carried in the headstock spindle.

40. Cutting Tools for Lathes
 Tools consists of cutting surface and support
 Cutting surfaces can be of same material as
support or a separate insert
 Supports materials must be rigid and strong
enough to prevent tool deflection during cutting
 Cutting materials are typically carbides, carbide
coatings, ceramics, or high carbon steels
 Inserts are used to decrease cost in that the insert
is disposed of, and the support reused.

41. Cutting Tools for Lathes
 External
 Right hand turning
 Left hand turning
 Round nose turning
 Cut-off
 Left hand facing

42. Cutting Tools for Lathes
 External (con’t)
 Broad nose finishing
 Right hand facing
 Threading
 Form
 Internal
 Boring
 Threading
 Grooving
 Form

43. Typical Tool Holders
FIGURE 22-16 Common
types of forged tool holders:
(a) right-hand turning,
(b) facing, (c) grooving cutoff,
(d) boring, (e) threading.
(Courtesy of Armstrong Brothers
Tool Company.)

44. Quick Change Tool Holders
 Tool changing can take
over 50% of manual lathe
operations
 Quick Change holders
are used to reduce
manual tool change time
and increase production

45. Workholding Devices for Lathes
 Work pieces can be
held by various
methods
 Work piece mounted
between centers
 Work piece mounted
within a single chuck
 Work piece mounted
within a collet
 Work piece mounted on a
faceplate

46. Lathe Centers
 A lathe center hold the end of the work piece, providing
support to preventing the work piece from deflecting
during machining
 Lather centers can be mounted in the spindle hole, or in
the tailstock quill
 Lathe centers fall into two categories
 Dead Center: solid steel tip that work piece spins against
 Live Center: centers contact point is mounted on bearings and
allowed to spin with work piece

47. Lathe Centers
FIGURE 22-21 Work being
turned between centers in a
lathe, showing the use of a dog
and dog
plate. (Courtesy of South Bend
Lathe.)
FIGURE 22-22 Live lathe
center can rotate with the part.

48. Lathe Chucks
 Lathe Chucks are adjustable mechanical vises that hold
the work piece and transfer rotation motion from the
drive motor to the work piece
 Lathe Chucks come in two basic types
 Three-jaw self-centering chucks
 Used to center round or hexagonal stock
 Four-jaw independent chucks
 Each jaw moves independently to accommodate various work piece
shapes

49. Lathe Chucks
The jaws on
chucks for lathes (four-jaw
independent or three-jaw selfcentering)
can be removed and
reversed.
Hydraulically
actuated through-hole three-jaw
power chuck shown in section
view to left and in the spindle of
the lathe above connected to
the actuator.

50. Face Plates

51. Mandrels

52. Lathe Collets
 Collets are used to hold round stock of
standard sizes
 Most accurate holding method for round
stock
 Run out less than 0.0005 inch
 Stock should be no more than 0.002 inch larger or
0.005 smaller than the collet
 Typically used for drill-rod, cold-rolled, extruded,
or previously machined stock

53. Lathe Collets
FIGURE 22-26 Several types
of lathe collets. (Courtesy of
South Bend Lathe.)

55. Summary
 Lathes are used for turning, boring, drilling
and facing
 Lathe typically holds the work piece in a
rotating chuck, with the opposite end
supported by a center held in the tailstock
 A wide variety of lathe types, and tool types
are available depending upon the application
and the rate of production
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