A needle roller bearing is a type of bearing that utilizes small cylindrical rollers that reduce the friction of a rotating surface. In comparison to ball bearings, needle roller bearings have a large surface area that is in contact with the functioning part. These are useful in manufacturing because of their ability to handle relatively high loads in a compact design. They are the smallest and lightest of the roller bearing family which gives them the advantage in limited space situations.
These bearings come in several different configurations including drawn cup, precision race, caged roller, and thrust roller bearings. The type that appears most often is the caged roller needle bearing. The caged roller bearings function is to support radial loads and rotational speeds. Developments to these bearings contour have been introduced to reduce roller-end stress from misalignment, or deflection, of one of their base balancing components (known as raceways). These developments enable a more uniform distribution of stress, optimizing the bearings performance. Typical applications for caged needle roller bearings are automotive transmission systems, two and four stroke engines, gearboxes, air compressors, and planetary gear sets.
Although these bearings often serve purposes elsewhere, they are typically designed to meet the specific needs of the aircraft industry in airframe manufacturing. Their design involves heavy outer rings to support high static, oscillating loads. These bearing rings and rollers are constructed of high-carbon chrome steel and are made with a protective finish. Some are intended to work as track rollers while others have applications in mounting housing. For heavier rolling loads, needle roller bearings are wider and have two rows of rollers. In situations with lighter rolling loads, only one row of rollers is needed.
Needle roller bearings are capable of higher load capacities than single-row ball bearings or roller bearings. They have the ability to handle larger, more rigid applications. Their excellent roller characteristics within a small cross section also add to their appeal. They are generally lower cost in comparison with other bearings as well. All of these attributes contribute to why needle roller bearings are a vital component in aircraft manufacturing.