The document discusses the centre lathe, including its parts, operations, accessories, tools, tool shapes, tool angles, tool holders, and cutting speeds. It provides details on chucks, centers, faceplates, steadies, and other accessories. Safety precautions are highlighted. Common lathe operations like turning, tapering, knurling and threading are explained. Recommended cutting speeds for materials like mild steel, stainless steel and aluminum are provided. Different types of cutting fluids are also summarized.

1. THE CENTRE LATHETHE CENTRE LATHE
PARTSPARTS
OPERATIONSOPERATIONS
ACCESSORIESACCESSORIES

2. SAFETYSAFETY
PRECAUTIONSPRECAUTIONS
• Always know the quickest way to stop the
machine.
• Never leave the chuck key in the chuck
• Clean the machine after every use.
• Oil the necessary parts before use.
• Never make any adjustment while the
machine is running.
• Never leave tools or scrap metals on the
machine.

3. Diagram used for illustrationDiagram used for illustration

4. LATHE TOOLSLATHE TOOLS
Lathe tools maybe made of any of the
following materials:
• Plain carbon steel
• High speed steel
• Stellite
• Cemented carbide
• Diamond

5. TOOL FORMSTOOL FORMS
BUTT BRAZED TOOLS
These are made by brazing or welding a
piece of H.S.S. to a high tensile steel
shank.

6. TOOL FORMSTOOL FORMS
TIPPED TOOL
These have a hip of cemented carbide, etc.
brazed to a blank of high steel. They are
very economical.

7. TOOL FORMSTOOL FORMS
TOOL BITS
These fit in a special holder that grips the
tool at an angle of 15 degrees. This
provides easy height adjustment.

8. TOOL SHAPESTOOL SHAPES
The shape of the tool and the angles of its
ground faces will depend on;
• The operation to be performed.
• The material which has to be machined.
• The power and rigidity of the lathe
• The amount of material to be removed.
• The quality of finish desired.

9. TYPICAL TOOLTYPICAL TOOL
SHAPESSHAPES

10. TYPICAL TOOLTYPICAL TOOL
SHAPESSHAPES

11. • .
TYPICAL TOOLTYPICAL TOOL
SHAPESSHAPES

12. TOOL ANGLESTOOL ANGLES
A large tool angle
• Gives maximum strength.
• Helps heat dissipation.
• Increases the power needed to force the
tool into the work.

13. TOOL ANGLESTOOL ANGLES
A small tool angle
• Weakens the cutting edges.
• Gives a good finish.
• Gives little tearing.
• Gives easy cutting.

14. TOOLSTOOLS
NB. The harder and tougher the material,
the more it will be for the cutting edge of
the tool to penetrate the metal, and at the
same time retain its sharpness.

15. Tool Angles.Tool Angles.
• .

16. PARTING OFF TOOLPARTING OFF TOOL
• .

17. STRAIGHT TOOL HOLDERSTRAIGHT TOOL HOLDER
This carries one tool which is held in
position by two or three set bolts. It is
locked in position by one large nut or
lever. Adjustment is made for height by
means of parallel packing pieces.

18. STRAIGHT TOOL HOLDERSTRAIGHT TOOL HOLDER
Advantages
• Sturdy and reliable
• The rake and clearance angles are not
affected when adjusting to center height.
Disadvantages
• Needs packing pieces for height adjustment.
• Will carry only one tool at a time

19. TOOL HOLDERTOOL HOLDER
This is a multi-tool post and holds four tools
at the same time. It is locked in by a single
hand lever. The holder swivels about its
centre bolt so that each tool in turn can be
brought into position.

20. THE MULTI-TOOL HOLDERTHE MULTI-TOOL HOLDER
Advantages
• Carries four tools at the same time.
• Height adjustment does not affect tool
angles.
Disadvantages
• Needs packing for height adjustment.

21. AMERICAN TYPE HOLDERAMERICAN TYPE HOLDER
This is usually on small lathes. Adjustment
for height is made by swiveling the boat or
rocker.

22. Advantages
• Height adjustment is easily made.
Disadvantages
• Only one relatively small bolt to lock the
tool box in position.
• The size of the tool that can be used is
limited by the width of the slot.
AMERICAN TYPE HOLDERAMERICAN TYPE HOLDER

23. CENTERING THE WORKCENTERING THE WORK
• .

24. ACCESSORIESACCESSORIES
TOOLS THAT ARE USED ON THE
CENTRE LATHE TO ENHANCE SOME
PROCESSES.

25. CENTERSCENTERS
These are machined with a morse taper, fit
into the morse taper sockets of the head
stock and tail stock spindles. Work to be
turned may be held between the two
centers or with chuck and tail stock in
center. They are usually made of H.C.S
but H.S.S, though expensive, is
sometimes used for heavy or high speed
work.

26. DEAD OR LIVE CENTERSDEAD OR LIVE CENTERS
The dead center fits into the tail stock and
the live center fits into the head stock.
Both have a 60 degree included angle at
the point, although this is sometimes
increased to 90 degrees for heavy work.

27. LIVE CENTRELIVE CENTRE
• .

28. HALF CENTERHALF CENTER
This is used in the tailstock to allow the tool
to clear the center and give more room for
facing up after the work has been
mounted between centers.

29. BALL CENTERBALL CENTER
This is sometimes used for tapering by the
“set-over tail stock” method. The standard
centers cannot sit squarely in the center
hole when the tail stock is set over.

30. THE LUBRICATION OF CENTERSTHE LUBRICATION OF CENTERS
Centers can be lubricated using the
following:
• Tallow
• Granite
• Grease

31. COLLET CHUCKSCOLLET CHUCKS
These are used to hold work to be turned
very firmly and will rotate it with a high
degree of accuracy.

32. COLLET CHUCKSCOLLET CHUCKS

33. CHUCKS AND KEYSCHUCKS AND KEYS
• .

34. FACE PLATEFACE PLATE
This is a circular slotted casting which
screws onto the spindle nose. It is used for
holding work that cannot be held
conveniently in the 3 or 4 jaw chucks or by
centers. Sometimes an angle plate has to
be used in the set-up, particularly when
two faces have to be machined at right
angles to each other.

35. FACE PLATEFACE PLATE

36. TRAVEL STEADYTRAVEL STEADY
This is bolted to the cross slide or carriage
of the lathe and is used to support long
slender work to stop the metal from
bending under the pressure of the cut.

37. TRAVEL STEADYTRAVEL STEADY

38. FIXED STEADYFIXED STEADY
This is bolted to the lathe bed and is used to
support work that projects a long way out
of the chuck. It is often used as an end
support for long bars too big in diameter to
go through the head of the machine, so
that end of the bar may be machined.
Grease is necessary where the jaws make
contact with the work.

39. FIX STEADYFIX STEADY
• .

40. FIXED STEADYFIXED STEADY
.

41. FIX STEADY IN USEFIX STEADY IN USE
• .

42. FIXED STEADY AT WORKFIXED STEADY AT WORK

43. PARTS OF THE LATHEPARTS OF THE LATHE
.

44. THETHE BEDBED
This is a casting, supported
on rigid legs and very
accurately machined on the
top faces. Different lathes
have differently spaced
beds.

45. THE GAP BEDTHE GAP BED
Many lathes are provided with a
gap in the bed at the headstock
end to accommodate work that
is short and larger in diameter
than can be swung over the
bed.

46. THE GAP BEDTHE GAP BED

47. BACK GEARBACK GEAR
Where a belt drive is used, a range
of low speeds is given often by
means of a back gear. If the lathe
has three pulleys, thus giving a
range of three spindle speeds,
back gear will provide three lower
speeds.

48. BACK GEARBACK GEAR

49. THE CARRIAGETHE CARRIAGE
This is a casting machined on the underside
to fit the bed and along which it slides.
Fixed to the front of the carriage is the
apron, behind which lies the mechanism
for controlling the movement of the
carriage and the cross slide.

50. CARRIAGECARRIAGE
• .

51. THE RACKTHE RACK
This is fitted to the underside of the bed
front. The carriage handle and spindle are
linked to the rack by gears so that when
the handle is turned the carriage moves
along the bed.

52. THE HEADSTOCKTHE HEADSTOCK
This is the casting fixed to the left hand end
of the bed.

53. THE HEADSTOCKTHE HEADSTOCK

54. THE CROSS SLIDETHE CROSS SLIDE
This is mounted on the carriage and can be
moved at right angles to the bed by
means of a hand wheel at the front.

55. COMPOUND SLIDE ORCOMPOUND SLIDE OR
TOPSLIDETOPSLIDE
This is mounted on the cross slide. It is
located by heavy dowel pin, on which it
swivels. The top of the cross slide is
marked in degrees so that the compound
slide can be turned and locked at any
desired angle.

56. SPEED CHANGINGSPEED CHANGING
• .

57. TAILSTOCK OR LOOSETAILSTOCK OR LOOSE
HEADSTOCKHEADSTOCK
This is a casting that can be moved along
the bed and locked in any desired position
by means of a locking nut or lever.

58. TAILSTOCKTAILSTOCK

59. TAILSTOCK OR LOOSETAILSTOCK OR LOOSE
HEADSTOCKHEADSTOCK

60. LEAD SCREWLEAD SCREW
ANDAND
FEED SHAFTFEED SHAFT
Running the length of the bed is the lead
screw, a threaded rod which can be turned
at different speeds by means of a gear
box or gear train.
This screw has threads of either square or
acme.

61. LATHE OPERATIONSLATHE OPERATIONS
• Facing
• Parallel turning
• Tapering
• Knurling
• Screw threading
• Drilling
• Boring
• Parting off

62. TAPER TURNING.TAPER TURNING.
• .

63. DRILLING ON THE LATHEDRILLING ON THE LATHE
• .

64. BORING ON THE LATHEBORING ON THE LATHE
• .

65. KNURLINGKNURLING
Knurling may be defined as the process of
checking the surface of a piece by rolling
depressions into the surface.

66. KNURLING TOOLKNURLING TOOL
Most knurled jobs in machine-shop are of
the pattern as fine, medium, coarse,
straight, and diamond. The knurls are
small wheels with the marking cut in their
faces and all are hardened.

67. KNURLSKNURLS
(1) and (4) coarse pattern, (2) and (5)
medium, (3) and (6) fine, (1), (2), and (3)
diamond, (4), (5), and (6) straight.

68. KNURLING OPERATIONKNURLING OPERATION
• .

69. Lathe Operations.Lathe Operations.
• .

70. Lathe Tools At WorkLathe Tools At Work

71. Cutting Speed.Cutting Speed.
• All materials have an optimumAll materials have an optimum
Cutting Speed and it is definedCutting Speed and it is defined
as the speed at which a point onas the speed at which a point on
the surface of the work passesthe surface of the work passes
the cutting edge or point of thethe cutting edge or point of the
tool and is normally given intool and is normally given in
meters/min.meters/min.

72. Cutting Speed.Cutting Speed.
Where:Where:
N = Spindle Speed (RPM)N = Spindle Speed (RPM)
CS = Cutting Speed of MetalCS = Cutting Speed of Metal
(m/min)(m/min)
d = Diameter of Work piece.d = Diameter of Work piece.

73. Recommended CuttingRecommended Cutting
Speeds.Speeds.
MaterialMaterial Cutting SpeedCutting Speed
Mild steelMild steel 18 to 2518 to 25
stainless steelstainless steel 12 to1812 to18
aluminiumaluminium Up to 300Up to 300

74. Cutting fluids inCutting fluids in
common use.common use.
• WaterWater
• It has a high specific heat but isIt has a high specific heat but is
poor in lubrication and alsopoor in lubrication and also
encourages rusting. It is used as aencourages rusting. It is used as a
cooling agent during tool grinding.cooling agent during tool grinding.

75. • They are used for heavier cutting
operations because of their good
lubricating properties and are
commonly found in production
machines where high rates of metal
removal are employed. Mineral oils
are very suitable for steels but should
not be used on copper or its alloys
since it has a corrosive effect.
Mineral Oils.Mineral Oils.

76. • Oil will not dissolve in water butOil will not dissolve in water but
can be made to form an intimatecan be made to form an intimate
mixture or emulsion by addingmixture or emulsion by adding
emulsifying agents. The oil is thenemulsifying agents. The oil is then
suspended in the water in the formsuspended in the water in the form
of tiny droplets. These fluids haveof tiny droplets. These fluids have
average lubricating abilities andaverage lubricating abilities and
good cooling properties.good cooling properties.
Soluble Oils.Soluble Oils.

77. Vegetable Oils.Vegetable Oils.
•They are goodThey are good
lubricants but are oflubricants but are of
little used since theylittle used since they
are liable toare liable to
decompose and smelldecompose and smell
badly.