Choose the basis of cooperation
According to the rotation of the imported bearing, there are three kinds of loads: local load, cyclic load and swinging load. Usually the cyclic load (rotating load) and swinging load adopt the tight fit; In general, it is not suitable to use tight fit for local load except for special requirements. When the imported 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 a little loose, should be able to do axial swimming in the hole of the imported bearing housing; When the imported bearing ring bears the swinging load and the load is light, a looser fit can be adopted.
(2) load size
The interference between the imported bearing ring and the shaft or shell hole depends on the size of load. When the load is light, a smaller interference fit is adopted. Generally, the radial load P is less than 0. When 07C is light load, P is greater than 0. So 07C is equal to or less than 0. Normal load at 15C, P is greater than 0. Heavy load at 15C (C is the rated dynamic load of the bearing).
Working temperature
When the imported bearing is running, the temperature of the collar is often higher than that of the adjacent parts. Therefore, the inner ring of the imported bearing may become loose with the shaft due to thermal expansion, and the outer ring may affect the axial swimming of the bearing in the shell hole due to thermal expansion. When helping to select the fit, the temperature difference, expansion and contraction of the part of the imported bearing device should be taken into account. 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 effect of elastic deformation and vibration, clearance fit should be avoided.
Bearing shell hole structure and material
For the hole of the form shell, it is not suitable to adopt interference fit when cooperating with the outer ring of the bearing, nor should the outer ring rotate in the hole of the shell. For bearings mounted on thin wall housing holes, light metal housing holes or hollow shaft, a tighter fit shall be adopted than thick wall housing holes, cast iron housing holes or solid shaft.
Easy to install and disassemble
For heavy machinery, bearings should be loose fit. When the tight fit is required, the separation type bearing, inner ring bearing with taper hole and tight set sleeve or back set sleeve bearing can be selected.
Axial displacement of the bearing
In the match, when one of the bearing ring is required to be able to move axial, the outer ring of the bearing and the hole of the housing of the bearing seat should adopt loose match.
Choice of match
The matching of the bearing with the shaft is base hole system, while the matching with the shell is base shaft system. The matching between bearing and shaft is different from the tolerance matching system adopted in the machine manufacturing industry. The tolerance band of bearing inner diameter is mostly below small change. Therefore, under the same matching condition, the matching ratio of bearing inner diameter and shaft is usually closely matched. Although the tolerance zone of bearing outer diameter and the tolerance zone of base shaft system are below zero line, their values are different from the general tolerance system.
