Radial and axial internal clearance and contact angle

Radial internal clearance (Gr)

The radial internal clearance is one of the most important bearing specifications and is not an indication of the quality of the ball bearing.
Without sufficient radial internal clearance, press fits (interference fits) and the normal expansion of the components cannot be absorbed without affecting the bearing. In extreme cases, this can cause the bearing to fail prematurely.

The radial internal clearance of an installed ball bearing influences the contact angle during operation, and thus the radial and axial load capacity, rigidity, service life, and other basic performance characteristics. Information on installation conditions that influence the radial internal clearance can be found in the section on shaft and housing tolerances. See also tolerances for shafts and housing seats.

A larger internal radial clearance is advantageous when high speeds generate more heat and when thrust loads occur. A smaller radial internal clearance is more suitable for predominantly radial loads.
The standard internal radial clearance of myonic radial ball bearings is between 6 and 15 μm (.0002″ to .0006″). If required, ball bearings can be supplied with larger or smaller internal radial clearances.

Please contact our application engineers. They will be happy to help you select the correct internal radial clearance for your specific application.

Axial internal clearance (Ga)

The axial internal clearance of a ball bearing corresponds to the total axial displacement of the inner ring relative to the outer ring under the influence of a low measured load.

Contact angle (α°)

The contact angle of a radial ball bearing or angular contact ball bearing is the angle between the plane perpendicular to the axis and the connecting line through the contact points of the balls on the raceways, after removal of the total radial internal clearance.

The contact angle is determined by the internal radial clearance, the size of the balls and the radius of the raceways. It increases slightly when an external axial load is applied to the ball bearings.

The standard contact angle of myonic radial ball bearings is between 17° and 22°.
The greater the contact angle, the greater the axial load capacity of the ball bearings, i.e. the ability to absorb axial loads increases.

Please contact our application engineers, who will be happy to help you choose the right contact angle for your application.