The Rolling Elements (Balls)

The function of the balls is to transmit the load through the bearing while allowing the shaft to rotate with minimal friction. The ball radius is slightly smaller than the raceway radius of the inner and outer rings. This allows the balls to contact the rings at a single point, appropriately called point contact. Ball dimensions are controlled to very tight tolerances. Ball roundness, size variations, and surface finish are very important attributes and are controlled to micro-inch levels (1 micro-inch = one-millionth of an inch).