Page 146 - Rollingbearings

B.6 Bearing interfaces
Tolerances for typically machined to the following tolerances are permissible The total run-out
tolerances: tolerances should be the same as for bear-
bearing seats and ings on cylindrical seats
• shaft seats to grade IT6 dimensional toler- Tolerance values for ISO tolerance grades
abutments ances and grade IT5 total run-out are listed in table 3
tolerances
• housing seats to grade IT7 dimensional
Dimensional tolerances for bearing seats are tolerances and grade IT6 total run-out
dictated by the required it Precision tolerances
requirements of the application will direct
you to which bearing tolerance class to use Suitable combinations of tolerance grades
(Bearing execution, page 182) and, conse- are listed in table 2 The tolerance zone for
quently, what run-out tolerance of the seat the total radial run-out is limited to half of
is needed The run-out of the seat is speci- the ISO tolerance grade, because the run-
ied by the total radial run-out of the seat out tolerance is speciied as a difference in
surface and the total axial run-out of the radii of two coaxial cylinders, and the ISO
abutment (ISO 1101, 18 16) tolerance grade refers to the diameter
For bearings with Normal tolerances in For seats of bearings mounted on with-
general industrial applications, seats are drawal or adapter sleeves, wider diameter

Table 2
Tolerance grades for bearing seats 1)

Application requirements Shaft seat Housing seat

A B
t 2 A-B
t 1 A-B
A B
Bearing interfaces d A d B D A D B

A-B
t 2
t 1 A-B
B.6

Dimensional Geometrical tolerance grades Dimensional Geometrical tolerance grades
tolerance tolerance
grade grade
Radial run-out Axial run-out Radial run-out Axial run-out
t 1 t 2 t 1 t 2

Bearing to Normal tolerances IT6 IT5/2 IT5 IT7 IT6/2 IT6
(moderate speed and running
accuracy)
Bearing to P6 tolerances IT5 IT4/2 IT4 IT6 IT5/2 IT5
(higher speeds or running
accuracy)
Bearing to P5 tolerances IT4 IT3/2 IT3 IT5 IT4/2 IT4
(high speeds and running
accuracy)

1) For very high-speed and high-precision applications, use SKF super-precision bearings and reduced IT tolerances (skf com/super-precision)

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