1.1—Differentiating Rolling Bearings

Rolling bearings are classified in several ways. In broad terms, bearing names reflect the load they support (radial or thrust/axial) and what kind of rolling elements are used (balls or rollers). They can be specified further by the shape of the rolling elements and how many rows are present, bearing size, whether the outer ring and inner ring are separated, and other characteristics.

Load Categories

A bearing’s contact angle (α) refers to the angle between an imaginary line perpendicular to the bearing axis and another through the points where a rolling element contacts the inner and outer ring raceway surfaces under load.
The size of contact angle α determines whether a bearing is a radial or thrust type.

Contact Angle and Bearing Type
Radial bearings: 0° ≤ α ≤ 45° (primarily radial loads supported)
Thrust bearings: 45° < α ≤ 90° (primarily axial loads supported)

α = 0°
(Examples of radial bearings)

2D cross-section of two radial bearings where contact angle α = 0. The contact points of the rolling element are aligned with a line through the center of the ball perpendicular to the axis of rotation.

Contact angle α
(Measurement, examples of radial bearings)

2D cross-section of a radial ball and a radial roller bearing indicating the angle between a line perpendicular to the center of the rotation axis and a line through the contact points of the rolling element.

α = 90°
(Examples of thrust bearings)

2D cross-section of a thrust ball bearing and a thrust roller bearing with 90° contact angle. At this angle, the bearing can typically only support loads parallel to the axis of rotation (thrust loads)

Rolling Element Categories

Ball Bearings

Deep groove ball bearing

Angular contact ball bearing

Self-aligning ball bearing

Roller Bearings

Tapered roller bearing

Cylindrical roller bearing

Spherical roller bearing

Number of Rows

Radial bearings are identified by the number of rows they have, with single-row, double-row, and multi-row varieties available.

Thrust bearings are additionally defined by the direction of loads they support, with single-direction or double-direction (multi-stage/tandem) variants available.