Typical fits of bearing nodes

The selection of a bearing node fit depends on the nature of the load, the direction of the load relative to the bearing rings, the speed of rotation and the operating conditions.

As a basic rule, the ring relative to which the load acts circumferentially should be seated with a push fit. The ring, relative to which the load is constant, can be seated with clearance or a transition fit.

Table of typical fits

Working conditions	Inner ring (shaft)	Outer ring (hole)	Nature of the fit
Normal load	k6	H7	Transition fit / light press fit
Heavy loads	m6	H7	Press
Very heavy loads / strokes	n6	H7	Powerful push
Outer ring stationary	h6	H7	Passing with ease
Circumferential load on the outer ring	h6	M7 / N7	Press in body
Fixing system	k6 / m6	H7	Axial fixation
Floating arrangement	k6	H7 (with axial play)	Expansion compensation

does not replace structural calculations

does not take into account the thermal expansion of materials with large α

does not apply to thin-walled bodies

Rules of interpretation

For a shaft that rotates relative to the load, the inner ring should have a push fit to prevent it from rotating on the settling surface.

If the load acts circumferentially on the outer ring, the pressure should be applied to the body seat.

For high dynamic loads, it is recommended to increase the push-in by selecting the m6 or n6 field.

Effect of temperature and speed

High rotational speeds and temperature differences between the shaft and the body can cause a change in the push-in value during operation.

Too much pressure can lead to a decrease in the radial clearance of the bearing and an increase in operating temperature. In such cases, the internal clearance class (e.g., C3) should be considered.

Construction Notes

The selection of a fit should be analyzed in conjunction with:

Geometric tolerance of settlement surfaces,
roughness,
The coaxiality of the sockets,
The method of assembly and disassembly.

Reference to standards

Selection of fits should be done in accordance with:

ISO 286-2 – dimensional tolerances
ISO 492 – bearing accuracy
ISO 1101 – geometric tolerances