Function of the Cage Prevent immediate contact between rolling elements to minimize friction and heat generation Guide the rolling elements Provide space for lubricant Retain the rolling elements when bearings of separable design are mounted or dismounted
The bearing internal clearance is defined as the total distance through which one bearing ring can be moved relative to the other under zero measuring load.
Why Internal clearance? In order to fit a bearing tightly on a shaft, it is necessary that the shaft is slightly larger than the bore of the inner ring. When the bearing is mounted, the inner ring will be expanded and consequently the space available for the rolling elements will be reduced. The reduction in space available for rolling elements when the bearing is mounted is accommodated by the internal clearance.
Why Internal clearance? Steel will expand with increased temperature. In operation, the temperature of the various parts of a bearing will not remain uniform and resulting in varying degrees of expansion which is compensated by the internal clearance.
Internal Radial Clearance Clearance range C1Clearance less than C2 C2 Clearance less than Normal C3 Clearance greater than Normal C4 Clearance greater than C3 C5 Clearance greater than C4 COLD WARM Reduced radial clearance Expansion Compression
The internal clearance required is dependent upon the mounting fit and the operating conditions. In case of doubt, a bearing with greater internal clearance shall always be selected.
Effect of Internal Preload and Clearance on Bearing Life Relative basic rating life L 10, % Preloading Clearance
Correct Fits Tolerance range for bearings manufactured to ISO
Operating conditions Available spaceMisalignment SpeedLife Load/Direction Bearing Selection Factors
International Organization for Standardization ISO ISO Standards
Relationship: Diameter and Width Series Diameter Series Width Series Height Series
Dimension Series Width Series Diameter Series
Bore diameter Written asExample Below 10 mm – 17 mm – 480 mm Above 500 mm 710/710241/710 Bore designation system
How the Designation System Works Bearing types Radial bearings, width (B, T)Thrust bearing, height (H) Outside diameter (D) Bearing size d/5 (30 mm bore diameter)