Needle bearings are roller bearings with cylindrical rollers, which are both thin and long relative to their diameter. This roller is called a needle roller. Although it has a small cross section, the bearing still has a high load bearing capacity, the needle bearing is equipped with a thin and long roller (roller diameter D≤5mm, L/D≥2.5, L is the length of the roller), so the radial structure is compact, its inner diameter size and load capacity are the same as other types of bearings, and the outer diameter is the smallest, especially suitable for radial installation size limited support results. According to the different occasions, bearings or needle roller and cage components without inner rings can be selected, and the journal surface and shell hole surface matched with the bearing are directly used as the inner and outer rolling surface of the bearing. In order to ensure that the load capacity and operating performance are the same as that of the bearing, the hardness, processing accuracy and surface quality of the shaft or shell hole raceway surface should be similar to the raceway of the bearing ring. Such bearings can only bear radial loads. The needle bearing with a stamped outer ring is a needle roller bearing with a thin stamped outer ring. The large size series of needle bearings have annular lubrication grooves and lubricating oil holes on the outer ring.
NA type：Both sides of the outer ring are equipped with elastic lock rings, and the inner ring has no guard edges. And there are two types of single row and double row needle rolling. The structure of NA type with inner ring or RNA type without inner ring can be made in either single or double row. The outer ring assembly (outer ring, needle roller and cage) of the NA type needle roller bearing is not separable, but can be separated from the outer ring assembly if there is no inner ring.
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