Needle Bearings
A needle roller bearing uses needle rollers, rather than balls, as its rolling elements. Sometimes the simpler term roller bearing or needle bearing is used instead. The term “needle” typically implies that the length is several times greater than the diameter.
Needle bearings have the advantage of greater load carrying capability vs. ball bearings. Theoretical contact is a line (needle roller bearings) compared to a point (ball bearings).
Key components are a cage (also known as a separator or retainer) and needle rollers. Other components, if they are present, essentially function as inner or outer races.
There are a wide variety of needle roller designs that Hartford Technologies produces. Plastic molded retainers coupled with bearing grade steel rollers are one option. Alternative needle roller bearing designs include a metal stamped cage and chrome steel needle rollers. Also, sometimes the cage / retainer is machined.
While in other cases, there is no cage. “Full complement” needle roller bearings use the maximum amount of rollers. Occasionally grease is used to hold the rollers in place until the needle roller bearing is assembled onto a shaft. In other cases, a temporary “plug” holds the bearing together until assembly. In yet other cases, the needle rollers hold each other together by virtue of their close proximity and geometry, similar to how a keystone works in a masonry arch.
