LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
shoulder. Lock the carriage and use the compound rest to feed the bit the
additional amount necessary to finish the workpiece to the proper length.
Engage the crossfeed to carry the bit away from the small diameter and face
the shoulder.
i.
Parting.
(1) General. One of the methods of cutting off a piece of stock while it
is held in a lathe is a process called parting.
This process uses a
specially shaped tool with a cutting edge similar to that of a square nose
cutting tool.
The parting tool is fed into the rotating workpiece,
perpendicular to its axis, cutting a progressively deeper groove as the
workpiece rotates. When the cutting edge of the tool gets to the center of
the workpiece being parted, the workpiece drops off. Parting is used to cut
off parts that have already been machined in the lathe, or to cut tubing and
bar stock to their required lengths.
(2) Parting Operation.
(a) The workpiece to be parted should be mounted in a chuck. In cutting
off stock, the setup of the tool should be made rigid. For the tool to have
maximum strength, the length of the cutting portion of the blade that
extends from the holder should be only slightly greater than half the
diameter of the work that is to be parted.
(b) Place the end of the cutting edge of the parting tool exactly on the
centerline of the lathe. To do this, place a center in the tailstock and
align the cutting edge of the parting tool with the tip of the tailstock
center. The workpiece should be held in the chuck jaws close to the point
at which the parting is to occur. Always make the parting cut and feed the
tool into the workpiece at right angles to the centerline of the workpiece.
The carriage is clamped to the bed to prevent the tool from moving to the
right or left when making a cut.
(c) The cutting speed is governed principally by the hardness of the
metal to be turned, the type of steel of which the parting tool is made, the
feed and depth of cut, the cooling medium used, the power and condition of
the machine being used, and the skill of the operator.
The recommended
starting speed is a spindle speed about one-third
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