Note that bearing manufacturers’ radial play values are given as a range. Tighter tolerance of the radial play may be specified, but it will increase the cost of the bearing since a sorting process is used to select specific radial play values.

Preload and Axial Play

In an application where accurate rotation is needed, the radial play must be removed from the bearing. Unless this is done, the races can bounce around relative to each other. The radial play is normally removed by using a pair of bearings which are preloaded to remove the play by pressing the races together axially until the balls are in firm contact with the raceways.

O-Type Preload Stiffer	X-Type Preload Less Stiff

Note that in the examples above, preload is achieved by pressing the inner races together (or outer races apart) to give O-type preload or by pressing the outer races together (or inner races apart) to give X-type preload. The O and X refer to the shape formed by the contact angle lines in the diagrams.