Thrust Roller Bearings
A thrust bearing is a particular type of rotary bearing. Like other bearings, they permit rotation between parts, but they are designed to support a predominantly axial load.
Thrust Roller Bearings are of three types:
- Cylindrical Roller Thrust Bearings
These bearings consist of small cylindrical rollers arranged flat with their axes pointing to the axis of the bearing. They give very good carrying capacity and are cheap, but tend to wear due to the differences in radial speed and friction which is higher than with ball bearings.
- Tapered Roller Thrust Bearings
These bearings consist of small tapered rollers arranged so that their axes all converge at a point on the axis of the bearing. The length of the roller and the diameter of the wide and the narrow ends and the angle of rollers need to be carefully calculated to provide the correct taper so that each end of the roller rolls smoothly on the bearing face without skidding. These are the type most commonly used in automotive applications (to support the wheels of a motor car for example), where they are used in pairs to accommodate axial thrust in either direction, as well as radial loads. They can support greater thrust loads than the ball type due to the larger contact area but are more expensive to manufacture.
- Spherical Roller Thrust Bearings
Spherical Roller Thrust Bearing is a self-aligning bearing. In service, it allows a maximum shaft misalignment of about 2 degrees. The contact angle helps this type of bearing to handle a small amount of radial load.
Lubrication of these bearings needs to be done carefully since their large sliding contact area results in smearing. Care should be taken to maintain at least rated minimum load on this bearing, to avoid smearing.