All rolling bearings consist of four parts: the outer ring, the inner ring, the rolling elements and the cage. Typically, the outer ring of a rolling bearing is mounted in a housing bore and remains stationary, whilst the inner ring is mounted on the shaft and rotates with it; the rolling elements roll between the raceways of the inner and outer rings, generating rolling friction.

1. Outer Ring

The outer ring usually forms a transition fit with the bearing housing or the bore of the machine casing, serving a supporting function.

2. Inner Ring

The inner ring usually fits tightly onto the shaft and rotates with it.

3. Rolling Elements

The rolling elements (balls, rollers or needles) are usually arranged evenly between the two rings within the bearing by means of a cage, performing a rolling motion. Their shape, size and quantity directly affect the bearing’s load-carrying capacity and performance.

4. Cage

In addition to evenly spacing the rolling elements, the cage also guides their rotation and improves the internal lubrication performance of the bearing. Cages can be classified into five types: wave-shaped cages, crown-shaped cages, E-shaped cages, solid cages and daisy-shaped cages.

5. Dust Covers and Seals

In addition to the four main components, some rolling bearings require dust covers or seals.

The function of a dust cover is to prevent external dust from entering the bearing.

Removable dust cover — commonly known as a ‘live cover’

Non-removable dust cover — commonly known as a ‘fixed cover’

The function of a seal is to prevent external oil, water or other media from entering the bearing.

Contact seals

Non-contact seals