the units or be carried into the bearing by the lubricant
while in service. Dirt may enter through seals, breather or
Excessive looseness under load is very objectionable
even dirty containers used for addition or change of
because it produces a creeping or slipping of the inner
ring on the rotating shaft. This causes the surface metal
of shafts to scrub or wear off.
Softer material such as dirt, dust, etc., usually forms
abrasive paste or lapping compounds within the bearings
Bearing fits on rotating shafts are usually specified as
themselves since the unit pressure between the balls and
tight. When play or looseness, even .001", exists
raceways makes a perfect pulverizer. The rolling motion
between the bearing and shaft, there is a very powerful
tends to entrap and old the abrasives. As the balls and
force tending to rotate the inner race on the shaft; this
raceways wear, the bearings become noisy. The lapping
force is caused by the looseness or lost motion between
action tends to increase rapidly as the fine steel from the
the parts and disappears when no looseness exists.
balls and rollway adds to the lapping material.
Removal of Bearings:
Hard, coarse material such as chips, etc., may enter
It is far more difficult to remove bearings from a shaft
the bearings during assembly from hammers, drifts,
than to put them on. In most cases it is necessary to
power chisels, etc., or be manufactured within the unit
remove the bearing by pulling on the outer-race which
during service from raking teeth, etc. These chips
can damage the balls or races. Since such damage is
produce small indentation in balls and races. Jamming of
seldom visible, it does not become known until after
these hard particles between balls and races may cause
complete reassembly. It is good P.M. to replace most ball
the inner race to turn on shaft, or the outer race to turn in
bearings during the overhaul period. If a bearing is not
going to be replaced, avoid removal during low mileage
All bearings are subject to fatigue and must be
replaced eventually. Your own operating experience will
All ball bearings (whether manufactured here or
dictate mileage replacement of bearings showing only
abroad) are interchangeable in regard to-standardized
dimensions, tolerances and fits. However, for a given
shaft size there are standard bearings for light, medium,
and heavy-duty service.
Water, acid and corrosive materials formed by
Numbers and symbols stamped on inner and outer
coating and small etched holes over outer and exposed
races of bearings designate size and type.
surfaces of race. Corrosive oxides also act as lapping
manufacturers, however, have not been standardized.
Brinelling caused by improper assembly or removal
usually hammering with off-center blows. Use drivers,
Consult interchangeable tables and use proper bearings
preferably under an arbor, or pullers.
for replacement parts.