The main parts of the ball bearing are the races and the balls. There is an outer and an inner race. The outer race goes into a bore, and the inner races carries the shaft. In between these two parts is where the balls are placed to create the bearing’s rolling properties.

Likewise, roller bearings follow suit with this placement. In both roller and ball bearings, the rolling element lies between the outer race and inner race. Then, there is a separator between the inner race and the outer race, in which the rolling element actually sits. On the inside of the inner race is where the shaft sits.

Without these basic parts, there is no ball or roller bearing.

There are, however, other bearing parts to consider such as flange, shield, and bore.

One additional part, for example, is the bearing cage, or retainer. All rolling bearings contain a cage. Depending on the number of ball or roller sets, the bearing may contain multiple cages. The purpose of the cage is to:

  • Reduce frictional heat in the bearing by separating rolling elements.
  • Evenly space the rolling elements to optimize load distribution.
  • Help avoid damaging sliding movements by guiding the rolling elements while in the unloaded zone.

Cages are stressed by friction, strain, and inertial forces, and can be degraded by high temperatures and certain chemicals. Thus, the design and material of a cage influence the suitability of a rolling bearing for an application. There are different types of cages for different bearing types and operating conditions. Below are three common types of cages.

Stamped Metal Cages: Typically made of sheet steel, stamped metal cages are lighter weight, and provide ample space inside the bearing to help maximize the effects of the lubricant.

Machined Metal Cages: Machined metal cages, typically made of brass or steel, generally permit higher operating speeds.

Polymer Cages: A third type of cage, the polymer cage, which is a fabric reinforced phenolic resin, has characteristics of both strength and elasticity. These cages are able to operate smoothly under poor lubrication conditions.