The tolerances of the inner ring bore diameter
and of the outside diameter of the inner ring
are defined in accordance with international
standards. The assembly conditions on the shaft
and in the housing are extremely important for
the correct functioning of a ball bearing.For the choice of adequate fits, it is therefore
very important to pay particular attention to
the following points.
Surface
finish and geometrical form of the shafts and
the housings
These
two parameters exert an influence over the fit
and the hearing noise partcuIarIy at high speeds
Temperature
and temperature variations
When
the shaft and the housing material are different
or with significant temperature variation, a change
of the Internal clearance may occur. The fit could
become either looser or completely blocked. Eventually,
length variation should be considered
Load
Range, direction and type
A
load increase requires tighter fits
Operating
conditions
Rotating
rings must have a tighter fit than fixed rings
In order to avoid any sliding
Rotational
accuracy and radial stiffness
High
requirements must be formulated In respect to
surface quality and geometrical forms
Influence
on the radial clearance
Inappropriate
tolerances on the shaft or the housing of a ball
bearing can lead to an expansion of the inner
ring, or to a narrowing of the outer ring. Consequence
may be a reduction or even a suppression of the
radial clearance
By taking the above mentioned points into
account and in order to get a Normal radial
clearance when assembling deep groove ball bearings,
machining tolerances of j5 to k5 for the shaft
and J6 for the housing are admissible.The dimensions of the abutments provided by
the shaft and the housing shoulder must be sufficient
in order to get a precise fit, an exact alignment
and an axial control with axial loads. On the
other hand the abutment surfaces should not
come into contact with the shields. The values
da mm and Da max for the abutment surfaces are
indicated in the bearing tables. These tables
also mention the minimum fillet radius rsmj,
of each ball bearing. The abutment surfaces
fillet radii must consequently be smaller than
ramin.
The following tables indicate the
machining tolerances of the shafts and the housings
allowing appropriate fits. The tolerances (in
jim and j.tinch) are only valid with shaft and
housing materials, which have the same expansion
coefficient as 100 Cr6 I SAE 52100 bearing steel
(11 x 10 m 1°C).
Fits are valid for normal operating
temperatures. At high temperatures, it is advisable
to check that the radial clearance is not too
high. In extreme conditions it is necessary to
try to find the best compromise.
Shaft fit tolerances
Housing fit tolerances