Basis for choosing cooperation

According to the rotation of the load acting on the imported bearing relative to the ring, there are three types of loads borne by the imported bearing ring: local load, cyclic load, and swing load. Usually, tight fit is used for cyclic loads (rotational loads) and swinging loads; Unless there are special requirements for use, tight fitting is generally not suitable for local loads. When the imported 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 slightly loose and should be able to move axially in the hole of the imported bearing seat housing; When the imported bearing ring is subjected to a swinging load and the load is relatively light, a slightly looser fit than a tight fit can be used.

(2) Load size

The interference fit between the imported bearing ring and the shaft or housing hole depends on the size of the load. When the load is heavy, a larger interference fit is used; When the load is light, use a smaller interference fit. Generally, the radial load P is less than 0. At 07C, it is a light load with P greater than 0. 07C is equal to or less than 0. At 15C, it is a normal load with P greater than 0. At 15C, it is a heavy load (C is the rated dynamic load of the bearing).

• Working temperature

When imported bearings are in operation, the temperature of the ring is often higher than that of adjacent parts. Therefore, the inner ring of the imported bearing may loosen from the shaft due to thermal expansion, and the outer ring may affect the axial movement of the bearing in the housing hole due to thermal expansion. When choosing a fit, the temperature difference and expansion/contraction of the imported bearing device should be taken into account. When the temperature difference is large, the interference fit between the shaft and the inner ring should be larger.

• Rotation accuracy

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

Structure and material of bearing housing holes

When fitting the shell hole with the outer ring of the bearing, interference fit should not be used, and the outer ring should not rotate inside the shell hole. For bearings installed on thin-walled shell holes, light metal shell holes, or hollow shafts, a tighter fit should be used than on thick walled shell holes, cast iron shell holes, or solid shafts.

Easy installation and disassembly

For heavy machinery, loose fit bearings are recommended. When a tight fit is required, separable bearings, inner ring bearings with tapered holes, and bearings with tightening or retraction sleeves can be selected.

Axial displacement of bearings

When it is required that one ring of the bearing can move axially during operation, a loose fit should be used between the outer ring of the bearing and the housing hole of the bearing seat.

The choice of cooperation

The fit between the bearing and the shaft adopts a base hole system, while the fit with the housing adopts a base shaft system. The fit between bearings and shafts is different from the tolerance fit system used in machine manufacturing. The tolerance zone of the bearing inner diameter is mostly below the loose change. Therefore, under the same fit conditions, the fit ratio between the bearing inner diameter and the shaft is usually tighter. The tolerance zone of the outer diameter of the bearing and the tolerance zone of the central axis in the base shaft system are both below the zero line, but their values are different from the general tolerance system.