Lathe machine

1. Unit 2 – CENTRE LATHE

2. HISTORY OF LATHE
STRAP LATHE:
• On these lathes the work-piece is held between two iron spikes supported by a
crude wooden framework. The tool rest is formed by a long rod, which runs
parallel to the axis. The motive power is transmitted by a strap which takes a
couple of turns around the end of the work-piece; the strap is pulled backwards
and forwards by the turner's assistant to provide a reciprocating motion. Usually,
both the turner and his assistant had to sit on the ground to operate this device.

3. HISTORY OF LATHE…..
BOW LATHE:
• The bow lathe is very similar to the strap lathe but the motive power is supplied by
a bow. The string of the bow is wrapped around the work piece and a reciprocating
motion is created by moving the bow backwards and forwards. Whereas the strap
lathe requires two people to work it the bow lathe requires only one. The
drawback is that less power is available and the turner has only one hand with
which to control the tool. In some cases the turner used his foot to help to steady
the tool. Because of these deficiencies only small work is done on the bow lathe.

4. HISTORY OF LATHE…..
POLE LATHE:
• The basic construction is shown in the diagram. It can be seen that the upper end
of the driving cord is attached to the tip of a flexible pole and the other end is
fastened to a simple treadle arrangement below the bed of the lathe. It should be
noted that function of the pole is to act as a return spring and to keep the string
taught-nothing more.

5. HISTORY OF LATHE…..
GREAT WHEEL:
• There is some evidence from a detailed examination of bronze vessels that the
Romans employed lathes using continuous motion. It has been suggested that the
drive could have been provided by means of a pulley system utilising an
independent "great wheel" as illustrated in Figure.

6. HISTORY OF LATHE…..
TREADLE LATHE:
• The turning speed for a treadle lathe was increased by using a flywheel and belt to
drive a small pulley on the headstock. Note that the flywheel and the pulley are
provided with a number of stepped grooves so that a variety of speed ranges could
be obtained by moving the belt.

7. PRINCIPLE OF LATHE MACHINE
• The lathe is a machine tool which holds the w/p b/w two
rigid & strong supports called centres or in a chuck or in
face plate which revolves.
• The cutting tool is held and fed against the revolving
work.
• Cutting tool fed either parallel or at right angles to the
axis of w/p or may also at an angle.

8. LATHE SPECIFICATION
• A-SWING
• B-DISTANCE B/W CENTERS
• C-LENGTH OF BED
• D-RADIUS(ONE HALF OF SWING

9. PRINCIPLE PARTS OF LATHE

10. PRINCIPLE PARTS OF LATHE
1-BED AND WAYS
• 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.

12. HEADSTOCK & SPINDLE
• The headstock comprises the rectangular metal casting at the left end of the lathe.
• It contains the spindle shaft and it supports bearings and high/low speed shift
lever and gears.
• Spindle is the main rotating shaft on which the chuck is mounted it supported by
precision thrust bearings.

14. TAILSTOCK
• 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.

16. CARRIAGE
• Carriage is located between the headstock and tailstock on the lathe bed guide ways.
• It can be moved along the bed either towards or away from the headstock.
• It has several parts to support, move and control the cutting tool.
• The parts of the carriage are :saddle, apron, cross-slide, compound rest, compound slide, tool
post.

19. SADDLE
• It is an “H” shaped casting. It connects the pair of bed guideways like a
bridge. It fits over the bed and slides along the bed between headstock
and tailstock. The saddle or the entire carriage can be moved by providing
hand feed or automatic feed.

20. CROSS-SLIDE AND COMPOUND REST
• Cross-slide is situated on the saddle and slides on the dovetail
guideways at right angles to the bed guideways. It carries
compound rest, compound slide and tool post. Cross slide
handwheel is rotated to move it at right angles to the lathe axis. It
can also be power driven. The cross slide hand wheel is graduated
on its rim to enable to give known amount of feed as accurate as
0.05mm.
• Compound rest is a part which connects cross slide and compound
slide. It is mounted on the cross-slide by tongue and groove joint. It
has a circular base on which angular graduations are marked. The
compound rest can be swiveled to the required angle while turning
tapers. A top slide known as compound slide is attached to the
compound rest by dove tail joint. The tool post is situated on the
compound slide.

21. CROSS-SLIDE AND COMPOUND REST

22. TOOL POST
• This is located on top of the compound slide. It is used to hold the tools
rigidly. Tools are selected according to the type of operation and mounted
on the tool post and adjusted to a convenient working position.

23. TYPES OF TOOL POST
• Single Screw Tool Post:

24. • Open side Tool post

25. • Four bolt Tool post

26. • Four way Tool post

27. Head Stock Mechanisms
• Back geared headstock

28. Head Stock Mechanisms
• Back geared headstock

29. Head Stock Mechanisms
• All geared headstock

30. Head Stock Mechanisms
All geared headstock

31. FEED MECHANISM
Tumbler gear reversing mechanism

32. Tumbler gear reversing mechanism

34. Quick change gearbox

35. Apron Mechanism

37. WORK HOLDING DEVICES
• Chucks:
Three jaw or self centering chuck:

38. • Three jaw or self centering chuck:

41. • Four jaw chuck:

42. • Four jaw chuck:

44. • Thin jobs can be held by means of
magnetic chucks.
Collet Chuck
Magnetic Chuck
Collet chuck is used to
hold small workpieces
Thin jobs can be held by
means of magnetic chucks.

45. Lathe Centers
 Work to be turned between centers must have center
hole drilled in each end
 Support during cutting
 Most common have solid morse taper shank 60º
centers, steel with carbide tips
 Care to adjust and lubricate occasionally

47. LATHE DOGS
• Lathe dogs are cast metal devices used to provide a firm connection
between the headstock spindle and the w/p mounted between centres.
Tail
Tail

50. MANDRELS
• Mandrels is used to held the hollow/drilled w/p
Workpiece Mandrel

52. RESTS
• Long w/p need extra support that tend to spring away from
the tool bit.
• We use the rest for provide support.
Jaws
Hinge
Work Work Jaws
Lathe bed guideways
Carriage

55. FACE PLATES
• A lathe face plate is a flat round plate that threads to the headstock
spindle to the lathe.
• The faceplate is used for irregularly shaped w/p that cannot successfully
held by chucks.
Workpiece

60. Lathe Operations
• Turning: produce straight, conical, curved, or
grooved work pieces
• Facing: to produce a flat surface at the end of the
part or for making face grooves.
• Boring: to enlarge a hole or cylindrical cavity made
by a previous process or to produce circular internal
grooves.
• Drilling: to produce a hole by fixing a drill in the
tailstock
• Threading: to produce external or internal threads
• Knurling: to produce a regularly shaped roughness
on cylindrical surfaces

61. Lathe Operations

62. THREAD CUTTING

63. TAPER TURNING METHODS
• Form tool method:

64. TAPER TURNING METHODS
• Tailstock set over method:

66. TAPER TURNING METHODS
• Compound rest method:

69. TAPER TURNING METHODS
• Taper turning attachment method:

72. TYPES OF LATHE
• Speed Lathe :
– It is the simplest type lathe. It is mainly used for metal
spinning, polishing etc.
• Bench Lathe :
– It is small sized engine lathe mounted on bench. It is used for
turning small and light weight workpiece.
• Tool Room Lathe :
• It is used for production of small tools, gauges, fixtures and
accurate parts in tool room.

73. TYPES OF LATHE
• Turret Lathe :
― These lathes are used in mass production and for heavy duty work
pieces.
• Capsten Lathe :
― These lathes are used in mass production used for light duty work
pieces.
• Special Purpose Lathe :
― These lathes are modification of engine lathes developed for
machining special types of work pieces.

74. ENGINE LATHE

75. BENCH LATHE AUTOMATIC LATHE

76. CAPSTAN AND TURRET LATHE
The turret lathe is a form of metalworking lathe that is used for repetitive
production of duplicate parts, which by the nature of their cutting process
are usually interchangeable.

77. CAPSTAN LATHE

78. TURRET LATHE

79. RAM OF CAPSTAN LATHE

80. SADDLE OF TURRET LATHE

82. S.No Capstan lathe Turret lathe
1 It is a light duty machine It is a heavy duty machine
2
The turret head is mounted on the ram and the
ram is mounted on the saddle.
The turret head is directly mounted on the saddle and the saddle
slides over the bed ways
3 The saddle will not be moved during machining The saddle is moved along with the turret head during machining
4
The lengthwise movement of turret is less
The lengthwise movement of turret is more
5
Short work pieces only can be machined.
Long work pieces can be machined
6
It is easy to move the turret head as it slides
over the ram
It is difficult to move the turret head along with saddle
7 The turret head cannot be moved crosswise The turret head can bbe moved crosswise in some turret lathes
8
As the construction of lathe is not rigid, heavy
cut cannot be given
As the construction of lathe is rigid, heavy cut can be given
9
It is used for machining work pieces up to
60mm diameter
It is used for machining work pieces up to 200mm diameter
10 Collet is used to hold the work piece Jaw chuck is used to hold the work piece

84. GENEVA MECHANISM
• The Geneva drive or Maltese cross is a gear mechanism that
translates a continuous rotation into an intermittent rotary
motion. The rotating drive wheel has a pin that reaches into a
slot of the driven wheel advancing it by one step.