Thrust roller bearings are composed of a thrust roller and cage assembly, wherein needle rollers or cylindrical rollers are configured radially in the cage, and a bearing ring of disc form is intended to support one-directional axial load.

In mounting, it is possible to use a shaft or a housing as the direct raceway surface without using the bearing, whereby design of a low height and lightweight compact construction is enabled. This type of thrust roller bearing results in slipping on raceway surface because theoretically it can’t roll perfectly, but in most cases it is practically trouble-free and can rotate at comparatively high speed. Current available bearing ring types are AS, WS, GS. The AS type consists of a thin steel disk having undergone surface-hardening, and can be used both on the shaft and in housing. Because of its 1 mm thick steel plate ring, this thrust bearing needs adequate rigidity and profile accuracy of machine parts adjacent to the bearing. As an individual, on occasion this thrust bearing results in slight camber, but it is flattened when specific thrust load acts thereon, having no problem in practical use. The WS and GS types are machined housing and shaft washers. Both provide high rigidity and running accuracy.