Most ball bearings are assembled in such a way that a slight amount of looseness exists between balls and raceways. This looseness is referred to as radial play and axial play. Specifically, radial play is the maximum distance that one bearing ring can be displaced with respect to the other, in a direction perpendicular to the bearing axis, when the bearing is in an unmounted state.

Axial play, or end play, is the maximum relative displacement between the two rings of an unmounted ball bearing in the direction parallel to the bearing axis. Since radial play and axial play are both consequences of the internal geometry of the components in a ball bearing, they bear a mutual dependence.

The contact angle is the angle between a plane perpendicular to the ball bearing axis and a line joining the two points where the ball makes contact with the inner and outer raceways. The initial contact angle of the bearing is directly related to radial play—generally, the higher the radial play, the higher the contact angle.

The parameters of radial play, axial play, and contact angle are all interrelated, and their values are all mathematically interdependent. Operating conditions, such as radial or thrust loading and bearing torque, must be considered when specifying one of the above, along with the effect on the other two parameters.

The extremes of the various parameters (i.e., radial play, axial play, or contact angle) are dependent upon manufacturing tolerances. Additional information about these interrelationships can be obtained by contacting a member of our Engineering staff.

Radial Play

Axial Play

Contact Angle