There are three kinds of loads that rolling bearing rings bear: partial load, cyclic load and swing load. Generally, tight fit is used for cyclic load (rotating load) and swing load; tight fit is not suitable for some loads except for special requirements. When the rolling bearing ring bears the dynamic load and is heavy load, the inner and outer rings should adopt interference fit, but sometimes the outer ring can be slightly loose, and it should be able to move axially in the bearing housing housing hole; when the bearing ring bears the swing load and the load is light, a slightly looser fit can be used.

The interference between the bearing ring and the shaft or shell hole depends on the load. When the load is heavy, the larger interference fit is used; when the load is light, the smaller interference is used. When the ordinary radial load p is less than 0.07c, it is light load, and P is greater than 0.07c and equal to or less than 0.07c. It is normal load at 15C, P is greater than 0. Heavy load at 15C (C is rated dynamic load of bearing).

Obligatory temperature

When the bearing is running, the temperature of the ring is often higher than that of the adjacent parts. Therefore, the inner ring of the bearing may loosen with the shaft due to thermal expansion, and the outer ring can affect the axial movement of the bearing in the shell hole due to thermal expansion. The temperature difference and the expansion and contraction of the bearing device should be considered when selecting the matching. When the temperature difference is large, the fit interference between the shaft and the inner ring should be larger.

Rotation accuracy

In order to eliminate the influence of elastic deformation and vibration, the clearance fit should be avoided when there is a high rotation accuracy requirement for automobile clutch bearing.

Structure and material of bearing shell hole

It is not suitable to use interference fit for housing hole and bearing outer ring, and the outer ring should not rotate in the shell hole. For bearings installed on thin-walled shell holes, light metal shell holes or hollow shafts, a tighter fit than thick walled shell holes, cast iron shell holes or solid shafts should be used.

Easy to install and disassemble

For heavy machinery, the bearing should be loose fit. When tight fit is required, differentiated bearing, tapered bore bearing with tightening sleeve or withdrawal sleeve can be selected.

Axial displacement of bearing

When a ring of bearing is required to move axially during operation, the outer ring of the bearing and the bore of the housing of the bearing housing shall be loosely fitted.

Choice of cooperation

The base hole system is used for the matching of bearing and shaft, and the base shaft system is used for the matching with the shell. The fit of bearing and shaft is different from the tolerance fit system adopted in machine manufacturing industry. The tolerance zone of bearing inner diameter is mostly below the change. Therefore, under the condition of adopting opposite fit, the matching ratio of bearing inner diameter and shaft is usually close. Although the tolerance zone of bearing outer diameter and that of shaft in base shaft system are both below the zero line, their values are not contrary to the common tolerance system.