15Function 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
21The bearing internal clearance is defined as the total distance through which onebearing ring can be moved relative to theother under zero measuring load.
22Why Internal clearance? In order to fit a bearing tightly on a shaft, it is necessarythat the shaft is slightly larger than the bore of the innerring. When the bearing is mounted, the inner ring willbe expanded and consequently the space available forthe rolling elements will be reduced. The reduction inspace available for rolling elements when the bearing ismounted is accommodated by the internal clearance.
23Why Internal clearance? Steel will expand with increased temperature. Inoperation, the temperature of the various parts of abearing will not remain uniform and resulting invarying degrees of expansion which is compensatedby the internal clearance.
24Internal Radial Clearance COLDReducedradialclearanceCompressionClearance range C1 Clearance less than C2 C2 Clearance less than Normal C3 Clearance greater than Normal C4 Clearance greater than C3 C5 Clearance greater than C4ExpansionWARM
25The 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.
26Effect of Internal Preload and Clearance on Bearing Life Relative basic rating life L10, %PreloadingClearance
27Correct FitsTolerance range for bearings manufactured to ISO
28Bearing Selection Factors Available spaceMisalignmentSpeedLifeLoad/DirectionOperating conditions
29International Organization for Standardization ISO StandardsISOInternational Organization for Standardization