Principles of bearing selection and application
Bearing specifics SKF super-precision bearings are manufactured to several general specifications. Those specifications concerning dimensions, tolerances, preload or clearance and materials are described in the following. Additional information is provided in each product chapter.
Boundary dimensions Boundary dimensions of SKF super-precision bearings follow the ISO 15 general plan for radial rolling bearings, or, in certain circumstances, conform to boundary dimensions accepted by industry. ISO 15 general plan The ISO 15 general plan for boundary dimensions of radial bearings contains a progressive series of standardized outside diameters for every standard bore diameter, arranged in a diameter series. Within each diameter series, different width series have also been established. Dimension series are formed by combining the number for the width series with the number for the diameter series.
For super-precision bearings, only a limited number of dimension series are used († table 3). Specific information about compliance to dimension standards is provided in each product chapter. Chamfer dimensions Minimum values for the chamfer dimensions († fig. 6) in the radial direction (r 1, r3) and the axial direction (r2, r4) are listed in the product tables. These values are in accordance with the general plans of ISO 15, ISO 12043 and ISO 12044. The appropriate maximum chamfer dimensions are in accordance with ISO 582 and are listed under Chamfer dimension limits.
Table 3 Diameter and width series for SKF super-precision bearings ISO 15 dimension series Diameter series Width series
SKF bearing series
Bearing type
8
1
718
Angular contact ball bearing
9
1
719
Angular contact ball bearing
4
NNU 49
Double row cylindrical roller bearing
1
70
Angular contact ball bearing
1 3
N 10 NN 30
Single row cylindrical roller bearing Double row cylindrical roller bearing
– –
BTW BTM
Double direction angular contact thrust ball bearing Double direction angular contact thrust ball bearing
2
0 0
72 BSA 2
Angular contact ball bearing Angular contact thrust ball bearing for screw drives
3
0
BSA 3
Angular contact thrust ball bearing for screw drives
0
46