The purpose of a ball bearing is to reduce friction that is rotational and it uses balls to maintain the separation between the moving parts. Ball bearings are used in a lot of devices simply anything that have a rotating motion may need ball bearings. Ball bearings are used in lot of devices like skates, hard discs, tools and different kinds of motors. If we do not use them in some mechanical devices, we will have to change the some parts constantly, as the friction is unavoidable. Generally the load that ball bearings bear, are divided into two categories which are radial and thrust, depending on the situation they are used.