Needle roller bearings are special roller bearings having slender cylindrical rollers that enable them to bear highest load capacity for a given radial space of all rolling-element bearings. Needle roller bearings are ideal for applications where high radial load carrying capacity is required but radial space is limited. Such bearings also suit applications where high rotational speed is involved but cannot accommodate axial loads. Compared to the ball bearings, needle bearing have a large surface area that is in contact with the bearing outer surfaces. Additionally they are more compact because there is less difference between the diameter of the shaft and the diameter of the bearing. Thrust needle bearings are flat and use a radial pattern of needles while radial needle bearings are cylindrical and use rollers parallel to the axis of the shaft. Needle bearings are primarily used in engine components like pumps, compressors, rocker arm pivots, and transmissions.
