Selecting a bearing

9. Internal Clearance

The internal clearance of a ball bearing affects life, noise, vibration, and heat generation.
It is important to select the appropriate internal clearance for each application.

Internal Clearance

The three types of internal clearance of a ball bearing are radial clearance, axial clearance, and moment clearance.

Radial Clearance (Gr)

The displacement generated by moving the outer ring in the radial direction while securing the inner ring (figure 9-1)

Axial Clearance (Gt)

The displacement generated by moving the inner ring in the axial direction while securing the outer ring (figure 9-2)

Moment Clearance (θ)

The angular displacement generated by tilting the inner ring in the axial direction while securing the outer ring (figure9-3)

Generally, radial clearance is considered as a specified value, as shown in the table below by NMB part number and JIS part number. When a ball bearing is fitted to either a shaft or housing with interference, internal clearance decreases.
The fits and temperature affect the internal clearance. Therefore, actual application conditions need to be reviewed when internal clearance is selected.

Radial clearance (Gr)
figure9-1

Axial clearance (Gt)
figure9-2

Moment clearance (θ)
figure9-3