The pretensioning methods are divided into two major categories: radial pretensioning and axial pretensioning. Here's a brief introduction:

Radial Pre-tensioning Method

Radial locking is commonly used in conical bore bearings that withstand radial loads, with the double-row precision short cylindrical roller bearings being a typical example. By adjusting the nut, the axial position of the bearing relative to the conical shaft neck is set, allowing the inner race to have an appropriate expansion and achieve radial negative clearance. This method is frequently employed in machine tool spindles and jet engines.

Harbin Bearing

Axial Pre-tensioning Method

Axial pretensioning methods can generally be divided into two types: positioning pretensioning and constant-pressure pretensioning.

In positioning pre-tensioning, the appropriate pre-tension can be achieved by adjusting the size of the bushes or shims; it can also be adjusted by measuring or controlling the starting friction torque; or, the pre-tension can be directly achieved using a pair of pre-tensioned double-connector bearings, which generally does not require further adjustment by the user. In summary, any bearing that has undergone axial pre-tension will maintain a consistent relative position during use.

Tensioning by constant pressure is a method of achieving proper preload in bearings using helical springs, disc springs, and the like. The stiffness of the preload springs is generally much lower than that of the bearing, so the relative position of the preload bearings will change during use, but the preload amount remains relatively constant.

The comparison between pre-tensioning for positioning and pre-tensioning for set pressure is as follows:

(1) When the preload is equal, the effect of positioning preload on increasing bearing rigidity is significant, and the change in rigidity during positioning preload also has a much smaller impact on bearing load.

(2) In service, the preload is affected by factors such as the axial length difference due to temperature differences between the shaft and bearing housing, radial expansion due to temperature differences between the inner and outer rings, and displacement caused by load, which can cause variations in preload; however, with fixed-pressure preload, the changes in preload are negligible.