1. WORKSHOP TECHNOLOGY 1
(JJ104)
Prepared by:
JKM PMS
7 August 2011
WORKSHOP TECHNOLOGY 1
JJ104

2. CHAPTER 5
LATHE MACHINE

3. OBJECTIVES
• Understand functions of parts of centre lathe
machine.
• Understand how work piece held to the lathe
machine.
• Understand shapes of tool bits and their function.
• Understand angles of a tool bit tip.
• Understand materials used in a tool bit.
• Understand lathe machine operation.

4. INTRODUCTION
Purpose :
• To rotate a part against a tool whose position it controls.
• Useful for fabricating parts and/or features that have a circular
cross section. The spindle is the part of the lathe that rotates.
Workholding attachments :
• Chucks, collets, and face plate can be held in the spindle.
• The spindle is driven by an electric motor through a system of
belt drives and/or gear trains.
• Spindle speed is controlled by varying the geometry of the
drive train.

5. INTRODUCTION (cont.)
Tailstock :
• Can be used to support the end of the workpiece with a
center, or …
• …to hold tools for drilling, reaming, threading, or cutting
tapers.
• It can be adjusted in position along the ways to accommodate
different length workpieces.
Machine Tool Basics - Intro to Lathe Operations - YouTube2.flv

6. PARTS OF LATHE MACHINE

7. PARTS OF LATHE MACHINE (cont.)

8. WORKSHOP TECHNOLOGY 1 JJ104
PARTS OF LATHE MACHINE (cont.)

9. PARTS OF LATHE MACHINE (cont.)
• Bed : - Supports all major components of the lathe.
• Carriage: - Slides along the ways and consists of an assembly
of the cross-slide, tool post and apron.
• Tool post: where cutting tools mounted
• Cross-slide: moves radially in and out, controlling the radial
position of the cutting tool
• Apron: equipped with mechanisms for both manual &
mechanized movement of the carriage and the cross-slide by
means of the lead screw
• Headstock: - Fixed to the bed and is equipped with motors,
pulleys and V-belts that supply power to spindle at various
rotational speeds.

10. PARTS OF LATHE MACHINE (cont.)
• Tailstock : - Can slide along the ways and be clamped at any
position, supports the other end of workpiece.
• Tail center: - To hold the end of long pieces of workpiece.
• Feed rod & lead screw: - The feed rod is powered by a set of
gears through the headstock. It rotates during the lathe
operation and provide movement to the carriage and the
cross-slide. Closing a half nut lever around the lead screw
engages it with the carriage.
• Chuck: - To hold the workpiece.

11. WORKHOLDING DEVICES
Introduction
• Workholding device is important, particularly in machine tools
and machining operations
• Must hold workpiece securely
• One end of the workpiece is clamped to the spindle by the
workholding device
• Types of workholding devices : Chuck, Collet, Face plate ,
Steady Rest, Follow Rest

12. 1. Universal Chuck - 3 Jaw Chuck
Use to hold a work piece which are cylinder or hexagon. For
facing or center drilling the end of the work piece.
Figure: Shows 3 positions 3 jaw chuck hold a work piece.
Be careful when use position (a) and (c) because the work
piece can easily slip when machining at high feed rate and high
depth of cut.
WORKHOLDING DEVICES (cont.)

13. 2.Independent chuck (4 jaw chuck)
Can hold work piece more precise rather than 3 jaw chuck.
Figure: Shows 3 positions 4 jaw chuck hold a work piece.
WORKHOLDING DEVICES (cont.)

14. 3.Collet chuck
Use to hold and machined small components
Generally for workpiece with a maximum diameter of
25mm
.
Figure: Collet chuck
WORKHOLDING DEVICES (cont.)

15. 4. Steady rest
Used to support a long workpiece which is 3 times its
diameter.
To prevent workpiece from bending
WORKHOLDING DEVICES (cont.)

16. 5. Follow rest
Suitable for small and long workpiece during parallel
lathe machining
To minimize flex under the pressure of the cutting tools
WORKHOLDING DEVICES (cont.)

17. 6. Face Plate
Used for clamping irregularly shaped workpieces.
The plates are round and have several slots and holes through
which the workpiece is clamped.
SmithyCo's Channel - YouTube.flv
WORKHOLDING DEVICES (cont.)

18. TO BE CONTINUE….
WORKHOLDING DEVICES (cont.)

19. Definitions:
• A piece of high-strength metal, usually steel, ground to
make single-point cutting tools for metal-cutting operations.
• In lathe, it refers to a non-rotary cutting tool and also often
referred to by the set-phrase name of single-point cutting
tool. The cutting edge is ground to suit a particular
machining operation and may be sharpened or reshaped as
needed. The ground tool bit is held rigidly by a tool holder
while it is cutting.
• Cutting tools must be made of a material harder than the
material which is to be cut, and the tool must be able to
withstand the heat generated in the metal-cutting process.
TOOL BITS

20. Various shape of Tool bit
TOOL BITS (cont.)
Figure: Standard Shapes

21. Various shape of Tool bit (cont.)
• Facing tools are ground to provide clearance with a
center.
•Roughing tools have a small side relief angle to leave more
material to support the cutting edge during deep cuts.
•Finishing tools have a more rounded nose to provide a
finer finish.
•Round nose tools are for lighter turning. They have no
back or side rake to permit cutting in either direction.
•Left hand cutting tools are designed to cut best when
traveling from left to right.
•Video
TOOL BITS (cont.)

22. 8/6/11
ANGLE OF TOOL BIT TIP
Figure: Single point cutting tools

23. 8/6/11
ANGLE OF TOOL BIT TIP (cont.)
Figure: Tool bit nomenclature

24. 8/6/11
Various angle in a cutting tool have important functions in
machining operation.
1. Rake angle: Control direction of chip flow and the strength of
the tool tip.
2. Side rake angle: Control direction of chip flow. Angle typically
about 5°.
3. Cutting-edge angle: Affects chip formation, tool strength, and
cutting force to various degree. Angle typically about 15°.
ANGLE OF TOOL BIT TIP (cont.)

25. 4. Relief angle: Control interference and rubbing at the tool-work
piece interface.
If it too large, the tool tip may chip off, if it too small, flank wear
may be excessive.
Relief angle typically are 5°.
5. Nose radius: Affects surface finish and tool tip strength.
The smaller the nose radius(sharp tool), the rougher the surface
finish of the work piece and the lower the strength of the tool.
How ever, long nose radius can lead to tool chatter.
ANGLE OF TOOL BIT TIP (cont.)

26. 1. Carbon steel
• Contain 0.9%-1.2% of carbon
• The oldest of tool material and widely use.
• Advantages: Cheap and easily shape and sharpened.
• Disadvantage: Do not have sufficient hot hardness and wear
resistance for cutting at high speed when the temperature rises.
2. High-speed steel(HSS)
• Contain: Tungsten, chromium, cobalt, molybdenum.
• Use to machine at higher speed, and complex such as drilling.
• Advantage: High toughness, resistance to fracture.
• Disadvantage: Low hot hardness.
TOOL BIT MATERIAL

27. TOOL BIT MATERIAL (cont.)
3. Stellite
• Contain 25%-35% chromium, 4%-25% Tungsten, 1%-3% carbon
and the rest is cobalt.
• Use for roughing cuts at high feed and speed-twice the rates
possible with HSS
• Advantage: high hardness, good wear resistance
• Disadvantage: not as tough as HSS and sensitive to impact
forces.

28. TOOL BIT MATERIAL (cont.)
4. Ceramic
• Consist of aluminium oxide.
• Moderately inexpensive
• Advantage: High hardness, high wear resistance, extremely resistant to
heat, desirable in high speed applications.
• Do not need coolant during machining.
• Disadvantage: High fragility. Ceramics are considered unpredictable
under unfavorable conditions. The most common ceramic materials are
based on alumina (aluminium oxide), silicon nitride and silicon carbide.
Used almost exclusively on turning tool bits. Hardness up to about HRC
93. Sharp cutting edges and positive rake angles are to be avoided.

29. 5. Carbide
• 2 major group of carbide (Tungsten Carbide and Titanium Carbide)
• Consist of 82% Carbide, 10% titanium and tungsten and 8% cobalt.
• Advantage: Very hard and can stand with high temperature
• Disadvantage: Low wear resistance
• Triple the rates possible with HSS (in term of cutting speed during
machining)
6. Diamond
• Use for surface finish
• High accuracy machining(0.002-0.005 mm)
• Disadvantage: easy fracture low impact resistance.
TOOL BIT MATERIAL (cont.)

30.  Turning: To produce straight, conical, curve or groove work
piece.
 Boring: To enlarge a hole or cylindrical cavity made by previous
process or to produce circular internal grooves.
 Facing: To produce flat surface at the end of the part and
perpendicular to its axis.
 Drilling: To produce a hole which may be followed by boring to
improve its dimensional accuracy and surface finish.
LATHE MACHINE OPERATION

31.  Knurling: To produce a regularly shaped roughness on cylindrical
surface(making knobs)
 Tread cutting: To produce external/internal threads.
 Off-centre turning: To produce various axis symmetric shapes
for functional or aesthetic purpose.
LATHE MACHINE OPERATION (cont.)