Page 123 - Turner 1st sem Practicals

Skill sequence

Parting off operation

Objective: This shall help you to
• set the parting off tool in the machine to the correct centre height
• follow the correct procedure while parting off
• observe certain precautions while parting off.

Parting off operation

Parting off or cutting off is the operation of severing a
finished part from the rough or finished stock.
Setting of parting tool

Set the parting tool exactly on the centre with as little back-
rake as possible. (Fig 1)

Set the spindle speed to half the speed for turning.
Move the carriage so that the right hand side of the blade
is at the point where the work is to be cut off. (Fig 4)

Adjust the parting off tool so that it extends one half the
diameter of the work plus about 3mm for clearance from the
tool-holder (Fig 2)

Start the lathe and feed the tool steadily into the work using
the cross-slide handle.
Continue to feed the tool into the work until the part is
severed.

Precautions
If the cutting tool is too high, it will not cut The work should protrude from the chuck jaws, sufficiently
through the workpiece. If it is too low, the work enough to permit the cut to be made as close as possible
may be bent and the cutting tool may be to the chuck jaws.
damaged.
The work must always be held securely in a chuck or a
Procedure collet.
Select the correct type of tool for a specified job. If the workpiece is held between centres, it
may bend or break and fly out of the lathe
Hold the work with the minimum overhang in a chuck.
during parting off. (Fig 5)
Set the tool square with the work so that it does not rub
against the sides of the groove, as it is fed into the work.
(Fig 3)
110 Producltion & Manufacturing : Turner - Exercise 1.3.35