Common Bearing Positioning Forms

In the shaft system, some shafts will expand and contract in the axial and radial directions due to working load, environment and speed. Some shafts, because they carry a large axial load, also need to transfer the load force to the frame. There are three common bearing positioning methods.

1. One-way fixation at both ends

In this positioning method, the inner ring of the bearing is fastened to the shaft neck by interference fit and blocked by the shaft shoulder, and the outer ring of the bearing is blocked by the bearing end cover. The bearings at both ends prevent the unidirectional movement of the shaft. In order to prevent the shaft from being stuck due to heat elongation, a gap of 0.2 to 0.3 mm is left between the end cover and the end face of the outer ring of the bearing for radial bearings; for radial thrust bearings, a set of gaskets between the end cover and the sleeve bearing seat are used to adjust the internal clearance of the bearing. This positioning method is suitable for short shafts with small torque transmission and low operating temperature.

2. One end is fixed in both directions and one end is free

The inner and outer rings of the bearing at one end are fixed in both directions and bear bidirectional axial forces. The bearing at the other end is not fixed axially, allowing the shaft that has expanded due to heat to stretch freely. Due to the different types of bearings, the structures of “bidirectional fixed” and “floating” are also different. Usually, the bearings subject to smaller radial forces are fixed in both directions to withstand the axial force and coordinate the life of the two bearings; when there is no axial force on the shaft, the bearings subject to smaller radial forces float to make the floating convenient. This positioning method is often used for shafts with large spans or shafts with high operating temperatures.

3. Swinging of supports at both ends

When a pair of herringbone gears are meshed, slight axial movement will occur due to manufacturing and installation errors. To prevent the gears from getting stuck, the two supports on the small herringbone gear shaft are often designed to float, and the two supports on the large herringbone gear shaft are fixed.

When the shaft support is a sliding bearing, the shaft is axially positioned by the shaft shoulder. When one end needs to be fixed, the shaft neck of the fixed end is made with shoulders or shaft rings on both sides, or a combination of radial sliding bearings and thrust sliding bearings is used.