Bearing radial play is a function of radial movement of the inner ring in relation to the outer ring. It is usually measured by holding the inner ring stationary and applying a radial load to the outer. Ball bearings are assembled with a slight amount of space between the balls and the raceways. This space represents the radial play. Radial play affects the performance in a given application by allowing the bearing to rotate smoothly with a predicable level of play. Radial play is a result of the bearing’s internal geometry. Therefore, the radial play value is a result of manufacturing tolerances. Radial play is measured perpendicular to the bearing’s axis of rotation while the bearing is unmounted from the final assembly. When properly measured, the radial play measurement yields the maximum displacement that one bearing ring can be located relative to the other. Generally, the inner ring is held in place on a shaft and the outer ring is moved radially for evaluation. Operating conditions must be considered when specifying radial play. Such factors as heat and lubrication can have a dramatic effect on radial play during bearing operation in the field.
Specified radial play should not be impeded, as this has an adverse effect on bearing life. The fit of the bearing on the shaft or in the housing will also impact bearing life. When the radial play is pushed below its specified level, discreet bearing components can become overheated, especially under extremely high running torque conditions. When the components become hot, the bearing retainer can cause catastrophic failure of the bearing. If that doesn’t happen, the retainer still may heat up enough to melt or become deformed. Then the retainer may rub on the bearing rings and begin flaking apart, causing debris and contamination to fall into the bearing components and result in premature bearing failure.
ABMA Standard Values for Radial Play
|Clearance Type||Range Designation|
|Tight .0001 inch to .0003 inch||K13|
|Normal .0002 inch to .0005 inch||K25|
|Loose .0005 inch to .0008 inch||K58|
|Extra Loose .0008 inch to .0011 inch||K811|
Other Radial Clearances Available Upon Request