1. Grease has impurities.
2. Insufficient lubrication (oil level is too low, improper storage may cause oil or grease to leak through the seal).
3. The clearance of the bearing is too small or too large (manufacturer problem).
4. Impurities such as sand or carbon particles are mixed into the bearing to act as an abrasive.
5. The bearing is mixed with moisture, acid or paint and other dirt, which acts as a corrosive effect.
6. The bearing is flattened by the seat hole (the roundness of the seat hole is not good, or the seat hole is not twisted straight).
7. The horn on the bottom of the housing is not flat (resulting in deformation of the seat hole or even cracks in the housing).
8. There are debris in the housing bore (residues, dust, etc.).
9. The seal is eccentric (touching adjacent parts and rubbing).
10. The bearing is subjected to an additional load (the bearing is axially tightened or there are two fixed end bearings on one shaft).
11. The bearing and the shaft are 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 the rotation is too tight (the tightening sleeve is too tight).
13. The bearing is noisy (caused by the end face of the roller or the slip of the steel ball).
14. The thermal elongation of the shaft is too large (the bearing is subjected to static and indeterminate axial additional load).
15. The shoulder is too large (touching the seal of the bearing and rubbing).
16. The shoulder of the seat hole is too large (the seal of the bearing is distorted).
17. The gap of the labyrinth seal is too small (friction with the shaft).
18. The teeth of the lock washer are bent (wearing the bearing and rubbing).
19. The position of the oil ring is not suitable (the flange cover is encountered and friction occurs).
20. There is a crater on the steel ball or roller (caused by hammering the bearing during installation).
21. The bearing is noisy (with external source interference).
22. The bearing is discolored and deformed by heat (caused by the use of a spray gun to disassemble the bearing).
23. The shaft is too thick to make the actual fit 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 bearing housing hole diameter 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 large (the housing hole of the non-ferrous metal is enlarged or enlarged due to thermal expansion).
27. The cage is broken.
28. The bearing raceway is rusty.
29. Steel ball, raceway wear (unqualified grinding or product scratches).
30. The ferrule raceway is unqualified (manufacturer problem).