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TM 5-4210-220-12
4-9 GENERAL MAINTENANCE PROCEDURES - Continued
e Fasteners
Replace any bolt, screw, nut, or fitting that has damaged threads. Inspect tapped holes for damage. If fitting
cannot be retapped with next oversize screw or stud, chasing the threads with proper size tap or die may cure the
problem.
f Gaskets
Never reuse old gaskets except in an absolute emergency. Always ensure correct gasket is being used as
replacement by fitting dry.
g Oil Seals
Install oil seals with lip seal facing the source of oil. Install by carefully applying an even force on the outer edge
of the seal. If oil seals are to be installed over a keyed or splined shaft, use a guide. This will prevent the sharp
edges of the shaft damaging the lip seal. Make a guide by cutting and shaping very thin gage sheet metal over
the splines. Make sure the edges are bent slightly inward to prevent these damaging the seal.
h Bearing Installation
CAUTION
To prevent personal injury or premature bearing failure when removing or installing bearing
races, always exert force on the tight ring of the bearing.
To assist in bearing installation procedures it is acceptable to heat or cool bearing races. Outer
bearing races can be cooled to reduce the race diameter. Place bearing in a deep freeze for
about two hours prior to assembly. It is acceptable to leave bearing in deep freeze for a longer
period of time.
CAUTION
To avoid bearing failure, never heat a bearing using an open flame.
Inner bearing races can be heated to increase the race diameter. An electrically-heated-type oil bath is
recommended. Do not allow oil temperature to exceed 275 deg. F (135 deg. C). The preceding procedure can
also be used to help during installation of gears on shafts. If accessible, shafts may be cooled to reduce outer
diameter, and gears may be heated to increase inner diameter.
j.
Lubrication
Lubricate bearings with the type of lubricant normally used before assembly (e.g. gear lube in gear box bearing).
This will provide lubrication during first run-in until system lubrication can reach bearings.
k Electrical Items
Replace broken, worn or burned electrical wiring with wire of the same carrying capacity. Always refer to tags
and sketches made at removal.
m Testing
Test operation of any system after installation or repair. Inspect for leaks, vibration, noise, misalinement or other
problems. Recheck after a few hours of normal operation.
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