Bearing interfaces

Performance and operating conditionsBearing type and arrangementBearing sizeLubricationOperating temperature and speedBearing interfacesBearing executionSealing, mounting and dismounting

Bearing seats on shafts and in housings, as well as components which locate a bearing axially, have a significant impact on bearing performance. To fully exploit the load carrying ability of a bearing, its rings or washers should be fully supported around their complete circumference and across the entire width of the raceway. Bearing seats should be manufactured to adequate geometrical and dimensional tolerances and be uninterrupted by grooves, holes or other features.
In this section you can find recommendations and requirements for designing bearing interfaces, including:
  • criteria when selecting bearing fits
  • recommended fits for standard conditions
  • tables to help determine minimum, maximum and probable values of clearance or interference between the bearing and its seat
  • recommendations for specifying geometrical tolerances of bearing seats
  • recommendations for the axial support of bearing rings
  • further design considerations for bearing interfaces

The ISO tolerance system

Fits for rolling bearings are typically specified with standard tolerance classes for holes and shafts as described in ISO 286-2. As bearings are typically manufactured to ISO tolerances (→ Tolerances), the selection of the tolerance class for the bearing seat determines the fit. Fig. 1 illustrates the position and width of the tolerance intervals of commonly used tolerance classes relative to the bearing bore and outside diameter tolerances. Fig. 1 is valid for bearings with Normal tolerances and of medium size. It is important to note that the ISO tolerance classes for rolling bearings and for holes and shafts are different. The tolerances for each size vary over the full range of actual sizes. You should therefore select the respective tolerance classes for bearing seats based on the actual bearing size for your application.
SKF logo