NEEDLE BEARINGS

Needle bearings use a roller style rolling element to reduce friction of a rotating surface. Needle Bearings have a high load carrying capacity with a very small cross section height. They are available with or without an inner ring. The needle rollers are guided parallel to the axis using a cage retainer, thrust bearings can also be supplied with no retainer, which is referred to as a full complement of rollers. 

Needle bearings have a larger surface area that is in contact with the bearing outer surfaces compared to ball bearings. Additionally there is less clearance, or the difference between the diameter of the shaft and the diameter of the bearing, so they are much more compact. The typical structure consists of an inner race (or sometimes merely a shaft), a needle cage which orients and contains the needle rollers, the needle rollers themselves, and an outer race. Needle bearings are heavily used in engine components such as rocker arm pivots, pumps, compressors, and transmissions.