Engineering Reference

Fits and clearances in bearings

The shaft and housing fits a bearing requires, which differ from general engineering fits.

Definition

Bearing fits are chosen for a different reason than structural fits: a rotating inner ring must not creep on its shaft, but the fit must not be so tight that it expands the raceway and closes the internal clearance.

Which ring rotates, and whether the load direction is stationary or rotating relative to it, determine the fit. That is why bearing manufacturers publish their own fit tables, and why following general H7/k6 guidance instead can be wrong.

Common misuse

Applying general engineering fit practice to a bearing seat. Bearing catalogues specify their own fits for good reasons.

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