Rolling bearings (as opposed to plain bearings which have no rolling elements) use balls or other rolling elements, located between bearing rings, to minimize friction. The rolling elements are separated and held in position by "cages" or other retaining devices.

Depending on the shape of their rolling elements, bearings fall into two main classes - ball bearings and roller bearings. Bearings are further classified by the specific shape of their rolling elements as ball, cylindrical, spherical, tapered. Bearings are also classified by function. For example, they can be classified as "radial," "thrust" or both, depending on the direction of the applied load.

Bearing Life
Many factors affect the life of roller bearings. These include assembly and mounting practices, preloading, lubrication, alignment and exposure to contamination or moisture. Adverse conditions in any of these areas may cause bearing failure. However, if precautions are taken to eliminate these potential trouble spots, the ultimate life of the bearing will be quite predictable.

Bearing Engineering
Bearing engineering ranges from research engineering to design engineering to application engineering.