How are the shafts and bearings connected?

On ultra high speed electric spindles, due to the increase in speed, there is a very high requirement for the dynamic balance of the components on the shaft. The 

positioning components of the bearings should not be connected to the main shaft through threaded connections, and the motor rotor should not be connected 

to the main shaft through key connections. Instead, removable stepped interference connections are commonly used.

This type of connection has significant advantages compared to threaded connections:

① Will not generate bending and torsional stress on the shaft, and has no impact on the rotational accuracy of the shaft;

② Easy to ensure the perpendicularity between the positioning end of the parts and the axis, so that the preloading of the bearing will not cause uneven force 

on the shaft and affect the service life of the bearing;

③ The quality of the interference sleeve is uniform, and the dynamic balance of the main shaft is easily guaranteed;

④ Generally, installation is carried out using the hot sleeve method, and disassembly is carried out by injecting pressure oil, which does not damage the main shaft;

⑤ Reliable positioning can improve the stiffness of the spindle.

When determining the basic interference fit of the stepped sleeve, in addition to calculating the required interference fit based on the load, the following factors 

should also be considered to affect the strength of the interference fit connection:

① The roughness of the mating surface;

② The difference between the working temperature of the connector and the assembly temperature, as well as the difference in the linear expansion coefficient 

between the spindle and the interference sleeve material;

③ When the spindle rotates at high speed, the centrifugal force acting on the interference sleeve will cause the expansion of the inner hole of the interference 

sleeve, resulting in a decrease in the interference amount. When the Poisson's ratio, elastic modulus, and density of the spindle material and the interference 

sleeve material are not significantly different, the corrected value of the interference amount is directly proportional to the square of the spindle speed.