Bearings-General bearings-Needle roller bearings
A needle bearing has a large surface area in contact with the outer surfaces compared to ball bearings, and is much compact as there is less added clearance. 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. Radial needle bearings are cylindrical and use rollers parallel to the axis of the shaft. Thrust needle bearings are flat and use a radial pattern of needles. Needle bearings are heavily used in engine components such as rocker arm pivots, pumps, compressors, and transmissions.