A bearing is a kind of mechanical structure which supports, shafts, axle, wheel or any rotating part of a machine.
They also reduces the friction between the parts whether the machine is the initial source of motive powers or it is driven externally. It depends upon the adequate lubrication and the friction reducing properties of the bearing themselves.
There are many types of bearings. They come in different forms such as the plain bearing, the ball bearing and the roller bearing.
The plain bearings are also known as the cylindrical journal bearing. It was assumed that these bearings were developed as the
same time as the wheel was invented. A chariot wheel rotating on its own axle is an example of an early type of plain bearing. Bronze and iron were speculated as the main constituents of these early bearings.The ball bearings are among of the bearings
which were termed as anti frictional bearing or rolling bearings.This bearings has three main element namely; the inner groove ring (also called race), the outer race and the steel balls. Steel balls were in between the races spaced in equal distant from one another in a cage that was made from other materials.
The part which constitute the inner race was being fastened to the shaft to be supported. The part which constitute outer race is secured to the stationary parts of the machine.
The roller bearings was also termed as anti-friction bearing. This bearing is closely related to the wheel.The development of these bearings were also dated probably from the development of the wheel itself.