NTN 608z Bearing
Needle Non Thrust Roller Bearings
Needle roller bearings utilize small, cylindrical rollers, referred to as needle rollers, to reduce friction between moving components. The needle rollers are the load-carrying components of the needle roller bearing. They are located between two races, between a single race and a shaft, or between a shaft and a housing, depending on the design of the bearing.
The rolling elements of a needle roller bearing have a large load-bearing surface, but a small diameter. Specifically, Mark's Standard Handbook for Mechanical Engineers defines needle roller bearings as, "a roller bearing with rollers whose length[s] are at least four times their diameter." The surface area of the rollers and the high number of rolling, load-bearing elements provide needle roller bearings with exceptional load capacity and stiffness.
Most radial needle roller bearings are designed to accommodate axial-oriented forces more than 5% of the radial load. Those which are used in radial applications have rollers that are parallel to the shaft. Thrust bearings, those meant for axial loads, contain rollers with axes that are perpendicular to the shaft and from which they extend radially.
All needle roller bearings require some type of lubricant to help dissipate heat and reduce friction. The amount of friction is resultant from the load carried, the type and size of the needle roller bearing, the speed at which the bearing rotates, and the characteristics of the lubricant used. Needle roller bearings, especially those with outer rings made of high-strength steels, can also suppress shock and vibration.