Needle roller bearings (4703 /IE) - SKF Magnetic Bearings - #23

Bearing internal clearance Is defined as the total distance through which one bearing ring can be moved relative to the other in the radial direction (radial internal clearance) or in the axial direction (axial internal clearance).

It Is necessary to distinguish between the internal clearance of a bearing before mount­ing and the internal clearance in a mounted bearing which has reached its operating temperature (operational clearance). The initial internal clearance (before mounting) is greater than the operational clearance because different degrees of interference in the fits and differences in thermal expansion of the bearing rings and the associated com­ponents cause the rings to be expanded or compressed.

The bearing internal clearance referred to as Normal has been selected so that a suit­able operational clearance will be obtained when bearings are mounted with the fits

usually recommended and operating con­ditions are normal. Where operating and mounting conditions differ from the normal, e.g. where interference fits are used for both bearing rings, unusual temperatures prevail etc., bearings with greater or smaller internal clearance than Normal are required. In such cases it is recommended that the residual clearance in the bearing after it has been mounted be checked.

SKF needle roller bearings with Inner ring are supplied as standard with Normal radial internal clearance, unless otherwise stated. Bearings having an internal clearance other than Normal are identified by the suffixes C2,C3andC4.

The limits for radial internal clearance correspond to ISO 5753:1991 and are given In Table Q.

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