1. There are impurities in the oil
2. Insufficient lubrication (oil level is too low, improper storage causes oil or grease to leak through the seal)
3. The clearance of the bearing is too small or too large (manufacturer's problem)
4. Impurities such as sand or carbon particles are mixed into the bearing, which acts as an abrasive.
5. The bearing is mixed with water, acid or paint and other dirt, which will cause corrosion
6. The bearing is flattened by the seat hole (the roundness of the seat hole is not good, or the seat hole is twisted and not straight)
7. The pad iron on the bottom surface of the bearing seat is uneven (causing deformation of the seat hole and even cracks in the bearing seat)
8. There are sundries in the bearing seat hole (residual chips, dust particles, etc.)
9. The sealing ring is eccentric (touching adjacent parts and causing friction)
10. The bearing is subject to additional load (the bearing is subject to axial tightness, or there are two fixed end bearings on one shaft)
11. The fit between the bearing and the shaft is too loose (the diameter of the shaft is too small or the adapter sleeve is not tightened)
12. The clearance of the bearing is too small, and it is too tight when rotating (the adapter sleeve is too tight)