LATHE OPERATIONS - OD1645 - LESSON 1/TASK 2
(4) Layout. Holes can be laid out using the cross feed of the lathe and
the vertical fed of the fixture. Use the compound feed to control the depth
and for locating the angular holes.
(5) Indexing.
(a) The workpiece is accurately indexed by use of the large graduated
collar. The method of centering the workpiece is as follows:
Step 1. Visually center the workpiece in the graduated collar and lightly
tighten the 3 set screws against the workpiece.
Step 2. Using a micrometer, measure across all three set screws (figure 35
on the following page). Total the 3 readings and divide them by 3.
Step 3. Loosen the top set screw and adjust the other two set screws to the
dimension outlined in step 2.
Lock these two set screws with jamnuts.
Tighten the top set screw against the workpiece. Recheck all three settings
with the micrometer.
Example: Using .751 diameter stock and with readings of 3.058, 3.085, and
3.071 totaling 9.214, and divide this reading by 3. The reading should be
3.071. The three set screws should be adjusted to the 3.071 dimension.
(b) When machining a quantity of like parts having exactly the same
diameter, two of the set screws can be kept securely tightened with the jam
nuts after centering the graduated collar for the first machined part.
After machining, the graduated collar is removed by loosening the screw
which does not have a locknut. The collar can then be used for machining
the remaining parts without having to measure the concentricity each time.
(6) Internal Keyway Cutting. Internal keyways are cut with the same type
of set-up as used for boring. The fixture is mounted on the lathe compound,
with the fixture plate parallel to the lathe bed. Mount the boring bar in
the V-groove keeping the tool slot of the boring bar in a vertical position,
so that the cutter may be brought up to the top position of the workpiece
bore. Use the lathe cross-slide to center the
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