Overview of bearing fastening

Tightening of inner ring

In order to fasten the inner ring of the bearing to the spindle, a thread is generally designed on the shaft, and a nut is used to position the bearing. The verticality between the axis of the nut thread and the end face and the matching accuracy of the thread are very important. If the manufacturing accuracy of the nut is not high, the nut will tilt after tightening, which is easy to cause the spindle to bend and the bearing preload to be uneven, which directly affects the rotation accuracy, rigidity and load-bearing capacity of the bearing. Therefore, in order to ensure the rotation accuracy of the shaft, the locking nut must be adjusted and tightened to prevent loosening. Corresponding to different preloads, the locking force applied by the bearing locking nut should be determined according to the actual working conditions and after testing.

In order to eliminate or reduce the influence of the positioning resistance of the parts during the assembly process, it is recommended that when locking the nut, first lock the nut with a torque of 2 to 3 times the normal locking force, then loosen the nut, and finally lock the nut with the normal locking force and tighten it. When using a locking nut, on the one hand, it is necessary to process the thread on the spindle; on the other hand, it is also necessary to match it with a high-precision nut, plus the rotation imbalance that is inevitably generated by the locking nut. Therefore, on the spindles of some high-speed precision CNC machine tools or machining centers, interference sleeves are used as axial positioning elements for bearings on the spindles.

Fastening of the outer ring

The outer ring of the bearing is mostly positioned in the bearing seat hole by bolts through the clamping end cover. If the tightening force of the bolts is too large or the end cover is unevenly stressed, the outer ring raceway of the bearing is prone to deformation. Therefore, the tightening force of the bolts must be controlled. In addition, in order to ensure the correct positioning of the outer ring of the bearing, the axial preload clearance between the clamping end cover and the end face of the bearing seat must also be controlled. It is recommended that the axial preload clearance between the clamping end cover and the end face of the bearing seat be controlled within the range of 0.01~0.04mm.