Four-point Contact Ball Bearings – Two in One: A four-point contact ball bearing can accommodate axial loads in both directions, in combination with radial loads up to a certain level, and provides a very tight axial shaft position tolerance. Also it saves space, because it can be seen as the combination of two single row angular contact ball bearings into one. Therefore, it is an excellent choice in applications such as industrial gearboxes, locomotive drives and compressors.
Four point contact bearings are single row angular contact bearings having a slight change in the construction compared to the angular contact bearing. This type of bearing normally tends to have contact at four points i.e. two in the outer race and two in the inner race.
Constructional Aspects:
The bearing consists of the following in its construction.
Solid outer rings of single construction
Split inner rings
The ball and the cage assemblies made of brass or polyamide cages.
The split inner ring tends to accommodate a large compliment of balls. The inner races are normally matched for that particular bearing alone.
The cage assembly is normally integrally assembled with the outer race.
The normal contact angle for the rolling elements and the cages is 35 degrees.
The bearings are suitable for working with minimum angular misalignments either in the housing bores or due to shaft deflections.
Due to the presence of split inner races, the bearings are not available in sealed or shielded condition.
Assembly Constraints:
The bearing must have a minimum axial load in order to work with low friction. In case of a low axial load, care should be taken to ensure the preloading of the bearing.
For cases where the four point bearing is used only as a thrust bearing, a large radial clearance must be provided in the housing for the outer race. This prevents the bearing from being subjected to any radial load.