Reference to Wikipedia, a bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis, or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts.

A rolling bearing, also known as a rolling element bearing, is a bearing which carries a load by placing rolling elements (such as balls or rollers) between two bearing rings called races. The relative motion of the races causes the rolling elements to roll with very little rolling resistance and with little sliding.

There are seven types of rolling elements that are used in rolling bearings: balls, cylindrical rollers, spherical rollers, gear rollers, tapered rollers, needle rollers, and toroidal rollers.

Ball bearing is a particularly common kind of rolling-element bearings. The ball bearing has inner and outer races between which balls roll. Cylindrical roller bearings are common which use cylinders as the rolling-element and used in small Speed Reducers.

Ball bearing
Ball bearing
Cylindrical roller bearing
Cylindrical roller bearing

Spherical roller bearing has an outer ring with an internal spherical shape. The rollers are thicker in the middle and thinner at the ends. Thus, spherical roller bearings can accommodate both static and dynamic misalignment. However, spherical rollers are difficult to produce and thus expensive, and the bearings have higher friction than an ideal cylindrical or tapered roller bearing since there will be a certain amount of sliding between rolling elements and rings. The spherical roller bearing are usually used in large Reduction Gearboxes.

Spherical roller bearing
Spherical roller bearing

The reduction gearboxes produced by Aokman are configured with the domestic bearings(such as HRB bearings, ZWZ bearings, Luoyang LYC bearings). But the gearboxes can be customized with foreign bearings(such as SKF, FAG, NSK, NTN and Timken Bearings, etc.) if the customers require.