Needle bearing is a kind of roller bearing with cylindrical roller. Compared with its diameter, the roller is thin and long. This kind of roller is called needle roller. Although the bearing has a small cross section, it still has a high load bearing capacity. The needle roller bearing is equipped with thin and long rollers (roller diameter D ≤ 5mm, L / D ≥ 2.5, l is the roller length), so the radial structure is compact. When its inner diameter and load capacity are the same as other types of bearings, the outer diameter is the smallest. It is especially suitable for the support structure with limited radial installation size.
The bearing without inner ring or needle roller and cage assembly can be selected according to different application situations. At this time, the journal surface and shell hole surface matched with the bearing are directly used as the inner and outer rolling surfaces of the bearing. In order to ensure the same load capacity and running performance as the ring bearing, the hardness, machining accuracy and surface quality of the shaft or shell hole raceway surface should be similar to the raceway of the bearing ring. This kind of bearing can only bear radial load.