LATHE OPERATION

INTRODUCTION:-
1)- Removing of additional metal from the job on lathe is called turning operation.
2)- The following different types of operation are performed for different types of work.
3)- There are two types of operation done by lathe machine a)- Common or Standard Operation, b)- Special or Rare Operation.

Common or Standard Operation:-
1. Facing,   2. Plain Turning,   3. Step Turning,   4. Eccentric Turning,   5. Taper Turning,   6. Boring,   7. Reaming,   8.Tapping,   9. Parting Off,   10. Knurling,   11. Form Turning.   12. Grooving and Under Cutting,   13. Thread Cutting.

Special or Rare Operation:-
This operation on lathe machine the job is gripped by the following methods:-               
1. Grinding,   2. Copying,   3. Relieving,   4. Milling,   5. Key-way,   6. Spring Winding        
7. Spinning.                                                  

1) Facing:-
i)- This is an operation of removing metal from the work face.
ii)- The feeding tool at right angle to the axis of the work.
Purpose of facing:-
i)- To have a reference plane to mark and measure the step lengths of the work.
ii)-  To have a face at right angle to the axis of the work.
iii)- To remove the rough surface on the faces of the work and have finished faces instead.
iv)- To maintain the total length of the work.
 Defects in Facing work:-
a)- Concave Face:- i)-This is caused by the tool digging into the work during the feeding as the tool is not clamped rigidly.
ii)-By clamping the tool rigidly with minimum overhang.
iii)- This defect can be avoided by clamping the tool rigidly with minimum overhang.
b)- convex face:- i)-This is caused by the blunt cutting edge of the tool.
ii)- The carriage not being locked.
iii)- To avoid this defect, re-sharpen the tool and use it; Also lock the carriage to the bed of the lathe.
c)- Pip left in the center:- i)- This is due to the tool  not  being set to the correct center height. By placing the tool to the center height,
ii)- This defect can be avoided by placing the tool to the center height.

2. Plain Turning:-

i)- Plain turning is the operation of removing excess amount of material from the surface of a cylindrical job.

ii)- Plain turning is done in two stages Rough turning and Finish turning.

Rough Turning:- 

i)- When more metal is to be cut from the metal in short time then it is called Rough Turning.

ii)- In this system job is rotated high speed for deep cut.

iii)- Normally cut deep is 2 to 5 mm and feed 0.3 to 1.5 mm.

Finish turning:- 

i)- For finish turning or finish cut high speed  with feed and cut less deep is required.

ii)- The finish proper quantity of coolant should be used.

iii)- sharp tool with round cutting edge is used.

3. Step Turning:- 

i)-It is an operation of producing various steps of different diameters in the work piece . 

ii)- This operation is carried out in the similar way as plain turning.

4. Eccentric Turning:-

i)- If any cylindrical job has two or more then two different types of axis and their centers are different from its axis then it is called Eccentric Turning.

5. Taper Turning:-  
i)-Taper is a gradual increase or decrease in the diameter dimension along its length of the job.
ii)-While specifying taper in drawings it should indicate the Angle of the taper  and Size of the component.
iii)- There are two classification of tapers a)-Self holding taper and b)-Quick releasing taper.
a)-Self holding taper:-
ii)-Self holding tapers have a smaller taper angle is limited to maximum 3 degree.
ii)- It does not have any locking device for holding the components assembled.
iii)- Example):- Taper shank of drill, reamers and sleeves.
b)-Quick releasing taper.
i)- This type of tapers have greater taper angles which require locking devices for holding.
ii)- Example):- Arbor of milling Machine.
Tapers are used for:-
i)- Self-alignment/location of components in an assembly.
ii)- Assembling and dismantling parts easily.
ii)-Transmitting drive through assembly.
Types of Taper:-
a)-Morse tape:-i)-Morse taper most commonly used standard taper in the industry.
ii)-It is self holding taper.
iii)-This taper is used for bores of spindle,nose of lathes and drilling machines,shank og drills,reamers,centers etc.
iv)-The Morse taper denoted by the letters MT.
v)-The included angle is approximately 3 degree and taper per foot is 5/8".
vi)- Its available from MT0 to MT7.
b)- Brown and sharp taper:- i)- Both quick releasing and self holding tapers are available in this taper.
ii)- The taper used in the arbors of a milling machine.
 c)- Jarno taper:- i)- This taper used in external taper of the lathe machine spindle nose where the chuck or face plate is mounted.
ii)- Its available from Nos 1 to No 20 and the amount Taper per foot id 0.6".
d)- metric taper:- i)- Both quick releasing and self holding tapers are available in this taper.
ii)- A self holding metric taper included angle is 2 degree 51'51" 
e)-pin taper:- i)- It is self holding taper.
ii)- It is available both in metric and British systems.
ii)- The amount of taper is 1:50 in metric system, and 1:48(1/4"TPF) in the British system.
iii)- it is used for Assemble parts which most be held, positioned for accurate quick and easy assembly and permits to transmits drive.
Methods of turning taper on lathe:-
The different method of taper turning on a lathe.a)- form tool method, b)- Compound slide method, c)- Tail-stock offset method, d)- Taper turning attachment method.