Needle roller bearings with thin and long roller (roller length of the diameter of 3 to 10 times the diameter is generally not more than 5mm), so the radial structure is compact, its internal diameter and load capacity and other types of bearings the same, The diameter of the smallest, especially for radial mounting size is limited by the support structure. Needle roller bearings according to the use of different occasions, the choice of non-inner ring bearing or needle roller and cage components, and bearings at this time to match the journal surface and shell The surface of the hole directly as the bearing inner and outer rolling surface, in order to ensure the load capacity and operating performance with the same ring bearing, shaft or housing hole raceway surface hardness, machining accuracy and surface quality should be used with bearing rings. Needle bearing is a combination of radial needle roller bearings and thrust bearing components of the bearing unit, compact structure, small size, high precision, can withstand a high radial load while under a certain axial load. And the product structure in various forms, adaptability, easy to install. Combination of needle roller bearings are widely used in machine tools, metallurgical machinery, textile machinery and printing machinery and other machinery and equipment, and mechanical system design can be very compact and smart.