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 calculated using

r = rop + Δrfit + Δrtemp + Δrother

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

The required minimum initial internal clearance value depends on the bearing type (→ Range of initial internal clearance).
For cross located single angular contact ball bearings, tapered rollers bearings or thrust bearings, ensure that the minimum value of the internal clearance set during mounting is equal to or greater than the required minimum initial internal clearance.
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.
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