1. The grease has impurities;

2. The cage is broken;

3. The bearing raceway is rusty;

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

5. Unqualified raceway of ferrule (problem of the manufacturer);

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

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

8. The sealing ring is eccentric (touching adjacent parts and causing friction);

9. There are sundries in the bearing seat hole (residual chips, dust particles, etc.);

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

11. The shaft shoulder is too large (touching the bearing seal and causing friction);

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

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

14. The shoulder of the seat hole is too large (it distorts the seal on the bearing);

15. The position of the oil slinger is not suitable (it touches the flange cover and causes friction);

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

17. Steel ball and raceway wear (unqualified grinding or product bruises);

18. The thermal elongation of the shaft is too large (the bearing is subjected to statically indeterminate axial additional load);

19. The bearing is clamped flat by the seat hole (the roundness of the seat hole is not good, or the seat hole is not straight);

20. The bearing is mixed with water, acid or paint and other dirt, which has a corrosive effect;

21. 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);

22. The clearance of the bearing is too small, and it is too tight when rotating (the adapter sleeve is too tight);

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

24. The bearing is discolored and deformed by heating (caused by disassembling the bearing by heating with a spray gun);

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

26. Insufficient lubrication (the oil level is too low, improper storage causes oil or grease to leak through the seal);

27. The shim on the bottom of the bearing seat is uneven (causing deformation of the seat hole and even cracks in the bearing seat);

28. The diameter of the bearing seat hole is too large and the actual fit is too loose (the bearing temperature is too high and the outer ring is slipping);

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

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