A needle bearing is a bearing which utilizes small cylindrical rollers. They are used to reduce friction of a rotating surface. Standard needle bearings are available in both inch and metric dimensions for bores as small as 4mm, while heavy duty needle roller bearings can accommodate bores up to 10”. Needle bearings have a large surface area that is in contact with the bearing outer surfaces (line contact) as compared to ball bearings (point contact). There is less added clearance in a needle bearing, making them more compact. The typical needle bearing consists of an inner race, a needle cage, which orients and contains the needle rollers, the needle rollers themselves, and an outer race. Often there is no inner race and the needle bearing rides directly on a shaft.
