LATHE OPERATIONS - OD1645 - LESSON 1/TASK 2
tightness or preload on the lead screw thrust bearings. To remove end play
between the cap and the lead screw, tighten the threaded retainer collar
until a slight binding in the bearings is felt.
Then lock the threaded
collar with the set screw.
3 The bronze lead screw threaded bushings control end play between
the lead screw and the main housing. The lower bushing is normally adjusted
by turning it to the left, after the set screws which lock the bushing in
place is released. Turn the bushing until a slight binding begins on the
lead screw.
4 If the threads become worn after extended rough usage, then
adjust the lead screw. This is accomplished by turning it to the right on
the opposite sides of the threads, which might bring them into use and
restore them to their original tightness and smoothness.
5 If
the
bushing
seats
before
sufficient
adjustment
is
accomplished, scribe a reference line on the bushing and the surrounding
casting.
Remove the lead screw, then remove the lower bushing, file or
grind from 1/32 to 1/16 inch from the inner end, and return the bushing to
its original place, lining up the threads by means of the reference line.
Replace the lead screw.
The bushing is now fully adjustable in both
directions.
(g) Adjusting the Bearings - Removing End Play.
1 The bearings are held in position and adjusted for end play by
the bearing retainers.
2 Worm bearings are correctly adjusted when they allow .004 inch to
.006 inch end play in the worm at room temperature and when a 50 pound end
thrust is applied to the worm. Overtightening the bearing will cause them
to heat and may cause eventual permanent damage.
3 End play in the main spindle is adjusted by the front bearing
retainer. Proper end play is obtained by tightening the retainer until the
bearings bind slightly while the spindle is turned lightly by hand.
The
retainer is then backed off just enough to free the bearing rotation.
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