A ball bearing is a type of rolling-element bearing which uses balls to maintain the separation between the moving parts of the bearing.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. Usually one of the races is held fixed. As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction than if two flat surfaces were rotating on each other.
Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.
Compared to other bearing types, the ball bearing is the least expensive, primarily because of the low cost of producing the balls used in the bearing.
Pillow block bearing
A pillow block bearing, also known as a plummer block, is a mounted bearing used to provide support for a rotating shaft with the mounting surface on a parallel line with the axis of the shaft. Housing material for a pillow block bearing is typically made of cast iron or pressed steel. Pillow block bearings are extensively used in conveyor systems such as tube chain conveyors. Most pillow block bearings are self-lubricating.
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