Miniature & small ball bearings

Internal Clearance

The internal clearance of ball bearings influences performance factors, such as life, vibration, sound and heat generation.
It is important to select the appropriate internal clearance for the application.

Internal Clearance

There are three types of internal clearance: "radial clearance", "axial clearance" and "moment clearance".

Radial clearance (Gr)

The displacement generated by moving the outer ring in the radial direction with the inner ring fixed (Fig. 9-1)

Axial clearance (Ga)

The displacement generated by moving the inner ring in the axial direction with the outer ring fixed (Fig. 9-2)

moment clearance (θ)

The angular displacement generated by tilting the inner ring in the axial direction with the outer ring fixed (Fig. 9-3)

Normally, the radial clearance is set as a standard value. The standard values using NMB symbol and JIS symbol, are shown in the table below.

If the ball bearing is press fit with the shaft or housing, the internal clearance is reduced.

The internal clearance changes depending on the fitting and temperature conditions, so it is necessary to select the internal clearance with consideration of the actual usage conditions.