According to the load acting on the bearing relative to the rotation of the ring, there are three types of loads endured by the rolling bearing ring: local load, cyclic load, and swing load. Generally, tight fits are used for cyclic loads (rotating loads) and swing loads; unless there are special requirements for use, local loads are generally not suitable for tight fits. When the rolling bearing ring is subjected to a dynamic load and a heavy load, both the inner and outer rings should adopt an interference fit, but sometimes the outer ring can be a little looser and should be able to move axially in the bearing housing hole; when When the bearing ring is subjected to swing load and the load is light, a slightly looser fit than a tight fit can be used.

Load size

The amount of interference between the bearing ring and the shaft or housing hole depends on the size of the load. When the load is heavier, a larger interference amount is used; when the load is lighter, a smaller interference amount is used. Generally, when the radial load P is less than 0.07C, it is a light load, when P is greater than 0.07C but equal to or less than 0. When 15C, it is a normal load, and when P is greater than 0. When 15C, it is a heavy load (C is the rated dynamic load of the bearing).

Operating temperature 

When the bearing is running, the temperature of the ferrule is often higher than the temperature of adjacent parts. Therefore, the inner ring of the bearing may become loose with the shaft due to thermal expansion, and the outer ring may cause thermal expansion that affects the axial movement of the bearing in the housing hole. When choosing a fit, the temperature difference and expansion and contraction of the bearing assembly part should be taken into consideration. When the temperature difference is large, the fit interference between the shaft and the inner ring should be larger.

Rotation accuracy

When high rotation accuracy is required for bearings, clearance fit should be avoided in order to eliminate the effects of elastic deformation and vibration.

Structure and material of bearing housing hole

For the formal shell hole, interference fit should not be used when matching with the bearing outer ring, nor should the outer ring rotate in the shell hole. For bearings installed in thin-walled housing bores, light metal housing bores, or hollow shafts, a tighter fit should be used than in thick-walled housing bores, cast iron housing bores, or solid shafts.

Easy to install and disassemble

For heavy machinery, bearings should use loose fits. When a tight fit is required, separate bearings, bearings with tapered holes in the inner ring and bearings with adapter sleeves or withdrawal sleeves can be used.

Axial displacement of bearing

In the fit, when one ring of the bearing is required to move axially during operation, the outer ring of the bearing and the housing hole of the bearing housing should adopt a loose fit.

Matching options

The cooperation between the bearing and the shaft adopts the base hole system, while the cooperation with the housing adopts the base shaft system. The fit between the bearing and the shaft is different from the tolerance fit system used in the machine manufacturing industry. The tolerance zone of the bearing inner diameter is mostly below zero. Therefore, under the same fit conditions, the fit ratio between the bearing inner diameter and the shaft is usually relatively tight. . Although the tolerance zone of the bearing outer diameter and the tolerance zone of the basic shaft system are both below the zero line, their values are different from the general tolerance system.