SKF - Rolling Bearings

Design considerations
Tolerances for tapered shaft seats
When a bearing is mounted directly onto a
tapered shaft seat, the tolerance grade of the
diam eter of the shaft seat can be wider than
the tolerance grade for a cylindrical seat.
Fig. 18 shows an IT9 grade diameter tolerance,
while the stipulated geometrical tolerance
is the same as for a cylindrical shaft seat.
For rolling bearings mounted on tapered shaft
seats, SKF recommends:
• The permissible deviation for the slope of
the taper should be a ± tolerance in accordance
with IT7/2, and is based on the bearing
width B († fig. 18). For design purposes,
the tolerance value has to be expressed in
degrees. The value can be determined using
IT7/2
D k = ——–
B
Table 11
Geometrical tolerances for bearing seats on shafts and in housings
d B d A D A
D B
A B
t 4 A-B
t 3 A-B
A
B
t 4
A-B
t 3
A-B
Surface
Characteristic
Symbol for
geometrical
characteristic
tolerance
zone
Permissible deviations
Bearings of tolerance class 1)
Normal, CLN P6 P5
Cylindrical seat
Total radial run-out t 3 IT5/2 IT4/2 IT3/2 IT2/2
Flat abutment
Total axial run-out t 4 IT5 IT4 IT3 IT2
Explanation
For normal
demands
For special demands with
respect to running accuracy
or even support
1) For bearings with a tolerance class higher than Normal (tolerance class P4 etc.), refer to Super-precision bearings
(† skf.com/super-precision).
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