Needle roller bearings are characterized by cylindrical rollers of very small diameter and relatively long length. Needle bearings are also called as “Quill bearings”. The length to diameter ratio of needles is more than four. That means if the diameter of the needle of needle bearing is 2 mm then the minimum length of the needle is 8 mm.
Rolling Contact Bearings, Their Types, and Applications.
Construction of Needle Roller Bearing
Needle bearings are used with or without inner and outer races. Very often, needle bearings are used without the races as shown in fig.
|Needle Bearing diagram|
In this case, the needles run directly on the surface of the shaft. The shaft is hardened and ground with a surface hardness of 50 HRC. This type of construction is suitable where limited radial space is available.
Materials for Sliding Contact Bearing.
Needle bearings advantages
- Needle bearings have a smaller outer diameter. It is due to this reason that they are often used to replace sleeve bearings. This allows replacement with little or no change in design.
- They are compact and lightweight compared with other types of bearings,
- They have a large load-carrying capacity, particularly at low peripheral speeds.
Applications of Needle Roller Bearings
Needle bearings are ideally suited for applications involving oscillatory motion such as piston pin bearings, rocker arms, and universal joints. They are also suitable for a continuous rotation where the load is variable or intermittent.
Bearing Materials and Their Desirable Properties.