Bearing tolerances

Bearings are manufactured to tight tolerances down to a thousandth of a millimetre depending on the bearing size and type. A term called “internal clearance” points to the relative movement of the outer to the inner ring. Interestingly, the internal clearance may be greater than the operational clearance specified for the bearing. This is because the interference fit locating the bearing either expands the inner ring or compresses the outer ring (or both), thereby reducing the internal clearance. The operating heat may also lead to thermal expansion that, in turn, can influence the internalclearance dimension.