Position Preload

A position preload is achieved by fixing two axially opposed bearings in such a way that a preload is imposed on them. Their positions, once fixed, remain unchanged while in operation. In practice, the following three methods are generally used to obtain a position preload:

1. By installing a duplex bearing set with previously adjusted stand-out dimensions and axial clearance
2. By using a spacer or shim of proper size to obtain the required spacing and preload.
3. By utilizing bolts or nuts to allow adjustment of the axial preload (In this case, the starting torque should be measured to verify the proper preload. )
4. When the inner rings of the duplex bearings shown in the figure are fixed axially, bearings A and B are displaced a0, and axial space, 2 da0 between the inner rings is eliminated. With this condition, a preload Fa 0 is imposed on each bearing. The relation between axial load, Fa, and displacement in a duplex set is shown in the following figure.