Bearing Mounting and Fitting: Bearing Preload in a Ball Bearing Pair || Dynaroll Bearing Design Factors Part 2

There are 3 methods typically used to achieve preload in a bearing pair.

1. Deadweight: A fixed weight is set against the bearing ring while adhesive cures to retain the bearings. This system is used in many applications, and gives well-controlled torque values as well as maximum stiffness. Disadvantages are cure time and special handling of adhesive in mass-production. Care must be taken to allow for relative thermal expansion effects if different materials are used in mating parts.

2. Spring: Spring is used to press inner rings together or outer races apart. This system is easy to assemble, but has minimal stiffness since the spring can move after assembly so that the stiffness of the final assembly is controlled by the spring rate rather than the raceway-ball elasticity. Thermal effects from relative expansions of mating parts are minimized. Spring preload is often used in high speed applications.

Note: For Belleville or wavy-washer springs the tolerance stack up of mating parts can give a variation in spring compression that is a large percentage of the maximum allowable compression of the spring. This means that the preload can vary greatly unless a spring with a low spring rate is used (can be difficult to find).

3. Solid clamping: Component parts are machined to precise dimensions to remove axial play when the races are clamped together. In theory, is easy to assembly has few components and good stiffness. However, due to the natural range of the bearing axial play, it is difficult to achieve in practice. Unless components and bearings are matched to a very high precision the resulting assembly may be damaged through raceway brinelling or may not have adequate preload

Note: precision matched bearing pairs are available as Duplex Pair Bearings, but these are significantly more expensive than standard bearings).

Bearing Mounting and Fitting, Page 7: Bearing Adhesives Information