Bearing basics

The advantages of rolling bearings

The friction of rolling bearing is very small , it can support and guide rotating or vibrating machine parts– such as shafts, axles or wheels – and transfer load between machine parts. Rolling bearing has the characteristics of high precision and low friction, so high speed can reduce noise, heat, energy consumption and wear. They are cost-effective and exchangeable machine elements that typically follow national or international dimension standards.

Basic types of bearings

The two basic types of rolling element distinguish the two basic types of rolling bearing:

        Rolling element is ball bearing, that is ball bearing;

        Rolling element is roller bearing, that is roller bearing.

Balls and rollers are different in how they make contact with the raceways.

Balls make point contact with the ring raceways. With increasing load acting on the bearing, the contact point becomes an elliptical area. The small contact area provides low rolling friction, which enables ball bearings to accommodate high speeds but also limits their load-carrying capacity.

Rollers make line contact with the ring raceways. With increasing load acting on the bearing, the contact line becomes somewhat rectangular in shape. Because of the larger contact area, the friction is higher, a roller bearing can carry a heavier load, but at a lower speed than a ball bearing of the same size.

Radial and thrust bearings

Rolling bearings are classified into two groups based on the direction of the load they predominantly accommodate: 

Radial bearings 
Radial bearings accommodate loads that are predominantly perpendicular to the shaft. Some radial bearings can support only pure radial loads, while most can additionally accommodate some axial loads in one direction and, in some cases, both directions. 

Thrust bearings 
Thrust bearings accommodate loads that act predominantly along the axis of the shaft. Depending on their design, thrust bearings may support pure axial loads in one or both directions , and some can additionally accommodate radial loads (combined loads). Thrust bearings cannot accommodate speeds as high as same-sized radial bearings.

The contact angle determines which group the bearing belongs to. Bearings with a contact angle ≤ 45° are radial bearings, the others are thrust bearings.