GRWs product catalouge

Fitting
The fits of the ball bearing on the shaft and
in the housing essentially determine the
operational behaviour of miniature ball
bearings. When selecting fitting tolerances,
the following criteria should therefore be
considered:
Rotation Conditions
Rings with circumferential loading should
have a tighter fit than rings with point
loading.
Circumferential loading occurs in the case of
rotating ring and stationary load or stationary
ring and rotating load. Point loading occurs
in the case of a stationary ring and stationary
load or rotating ring and rotating load.
The values shown in tables 12 and 13 are only
valid for materials with similar thermal expansion
coefficients (11 · 10 -6 · K -1 ).
If the expansion coefficient varies or if there
are temperature variations between the outer
ring and housing or between the inner ring
and shaft, tolerances which ensure the
appropriate fit at operating temperatures
should be selected.
Running Accuracy
The same high standard of accuracy and
surface quality expected of the bearing must
be applied to shaft and housing.
Loading
Higher loads demand tighter fits.
Temperature
There may be temperature differences
between the ball bearing and mating
components while the ball bearing is in
operation. The dimensional changes caused
by differential expansion should be taken into
consideration.
In the case of miniature bearings great
importance is placed on simple mounting and
high running accuracy, hence only a close
sliding or transition fit is usually possible.
Furthermore it must be remembered that
irregularities on the shaft or in the housing
bore are transferred to the relatively thinwalled
bearing rings. In order to improve the
fit, it is possible to calibrate the bore and
outside diameter into groups (see page 58).
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