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)

Radial clearance (Gr)
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)

Axial clearance (Ga)
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)

Corner clearance (θ)
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.

Radial clearance of NMB numbering system

Clearance symbols

P13

P24

P25(standard)

P58

Clearance amount (μm) 2.5~7.5 5.0~10.0 5.0~12.5 12.5~20.0

Radial clearance of JIS numbering system

Clearance symbols

M2

M3(standard)

M4

M5

Clearance amount (μm) 3~8 5~10 8~13 13~20

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