1. Grease has impurities;

2. Insufficient lubrication (oil level is too low, improper storage leads to oil or grease leakage through the seal);

3. The clearance of the bearing is too small or too large (problem of the manufacturer);

4. Impurities such as sand or carbon particles are mixed into the bearing to act as an abrasive;

5. Moisture, acid or paint and other contaminants are mixed into the bearing to play a corrosive role;

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 horn on the bottom surface of the bearing seat is uneven (causing deformation of the seat hole or even cracks in the bearing seat);

8. There are debris in the bearing housing hole (remains of cuttings, dust particles, etc.);

9. Eccentricity of the sealing ring (touching adjacent parts and causing friction);

10. The bearing is subjected to additional load (the bearing is axially tightened, or there are two fixed-end bearings on a shaft);

11. The fit of 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);

13. The bearing is noisy (caused by the end face of the roller or the steel ball slipping);

14. The thermal elongation of the shaft is too large (the bearing is subjected to static and additional axial load);

15. Shaft shoulder is too large (touching the bearing seal and friction);

16. The shoulder of the seat hole is too large (the seal made by the bearing is distorted);

17. The gap of the labyrinth seal ring is too small (friction with the shaft);

18. The teeth of the lock washer are bent (touch the bearing and friction occurs);

19. The position of the oil rejection ring is not suitable (touching the flange cover and friction);

20. There are pressure pits on the steel ball or roller (caused by hitting the bearing with a hammer during installation);

21. The bearing is noisy (with external vibration source interference);

22. The bearing is discolored and deformed by heat (caused by heating the gun to remove the bearing);

23. The shaft is too thick and the actual fit is too tight (causing the bearing temperature to be too high or noise);

24. The diameter of the seat hole is too small (causing the bearing temperature to be too high);

25. The diameter of the bearing seat hole is too large, the actual fit is too loose (the bearing temperature is too high-the outer ring slips);

26. The bearing housing hole becomes larger (the bearing housing hole of non-ferrous metal is enlarged or becomes larger due to thermal expansion);

27. The cage is broken.

28. Bearing raceway rust.

29. Steel ball, raceway wear (unqualified grinding or scratched product).

30. The ferrule raceway is unqualified (problem of the manufacturer)