Thrust bearings is a particular type of rotary bearing, they are designed to support a predominantly axial load.Thrust bearings come in several varieties,Thrust ball bearings, Cylindrical thrust roller bearings ,Tapered roller thrust bearings, spherical roller thrust bearing. The thrust ball bearings are classified into two kinds: unidirectional thrust bearing and bidirectional thrust bearing. The former can bear the axial force in one direction and the latter can bear he axial forces in two directions. Both unidirectional and bidirectional thrust ball bearings cannot bear any radial force. Thrust ball bearing can limit axial displacement of shafts or housings in one or two direction, but not radial displacement. Therefore, the bearings are usally used with deep groove ball bearings. Generally, the cylindrical roller thrust bearing has one or two rows of rollers, and can bear a considerable axial force as well as a certain vibration load. The structure does not have the radial locating function and cannot bear any radial force, and in addition, it has no self-aligning function.