A bearing is a machine element that constrains relative motion and reduces friction between moving parts to only the desired motion. The design of the bearing provide free linear movement of the moving part or for free rotation around a fixed axis; Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts and some variants of the same are: Ball bearings, taper roller bearings, cylindrical bearings, needle roller bearings etc.