Required minimum initial internal clearance

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

The required minimum initial internal clearance can be estimated using

r = rop + Δrfit + Δrtemp + Δrother

required minimum initial internal clearance [μm]
required operating clearance [μm]
Δrfit clearance change caused by the maximum expected fits [μm]
Δrtemp maximum clearance change expected from the temperature difference during start-up or in steady state [μm]
Δrother maximum clearance change expected from other effects such as axial clamping

  • Bearing types for adjusted bearing arrangements – such as angular contact ball bearings, tapered roller bearings or spherical roller thrust bearings – have their internal clearance set during mounting (→ Mounting adjusted bearing arrangements).
  • For other bearing types, select a bearing clearance class (Normal, C3, C4, etc.) whose minimum clearance is equal to or greater than the estimated minimum initial internal clearance (fig. 1). Then verify whether the resulting maximum clearance of the selected clearance class is acceptable for the application. If the maximum clearance, for whatever reason, is too large then consider choosing a reduced clearance group – e.g. C3L, which includes only the lower half of the C3 clearance group range.
SKF logo