LATHE OPERATIONS - OD1645 - LESSON 1/TASK 2
respective brush holders if they are long enough for additional use. Each
brush should be returned to its exact position as before removal to prevent
changes in the brush seating. Brushes should be replaced when worn to 1/4
inch in length.
(b) Whenever brushes are replaced, the commutator should be turned down
and undercut.
New brushes on a badly worn commutator will spark
excessively, giving very little life.
3.
Metal Cutting Lathe Fixture
a.
General.
(1) The metal cutting lathe fixture is a work holding device which mounts
on the compound of a conventional lathe (figure 34 on the following page).
Machining is accomplished with the cutter held in the chuck or collet of the
lathe spindle. The fixture provides vertical travel which is used with the
longitudinal and traverse of the lathe.
Power feed and a wide range of
spindle speeds are already built into the lathe.
(2) Capacities of the fixture are 2 inch diameter round stock and up to 2
inch square in flat stock. The length of stock is unlimited.
b.
Installation.
(1) General. The metal cutting lathe fixture is a precision tool. It can
not be more accurate than the lathe on which it is being used.
Before
mounting the fixture, check the lathe compound. Remove any burrs or surface
irregularities with a file and check the top of the compound for trueness in
both directions of travel. Compounds on most lathes are true to within .001
inch in either direction, and this is acceptable for use with the fixture.
Mount the fixture on the lathe following these procedural steps:
Step 1. Slide the fixture onto the compound with the T-slot mounting clamp
in the T-slot of the compound and lightly tighten the mounting screws.
Step 2. Bring the fixture plate into full contact with the lathe faceplate
or face of the lathe spindle as shown in figure 34 to align the fixture
laterally. This provides adequate alignment for
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