1. The NTN bearing is mixed with impurities such as sand or carbon particles to act as an abrasive.
2. The NTN bearing is mixed with moisture, acid or paint and other dirt, which acts as a corrosive effect;
3. The clearance of the NTN bearing is too small (the selection is not appropriate);
4. The lubricating oil or grease type is incorrectly selected;
5. Insufficient lubrication (oil level is too low, oil or grease leaks through the seal);
6. The NTN 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 of the bottom surface of the NTN bearing housing is not flat (resulting in deformation of the seat hole or even cracking of the NTN bearing housing);
8. There are debris in the hole of the NTN bearing housing (residual chips, dust particles, etc.);
9. The seal is eccentric (wearing adjacent parts and rubbing);
10. NTN bearings are subjected to additional loads (NTN bearings are axially tightened, or two fixed-end NTN bearings on one shaft);
11. The thermal elongation of the shaft is too large (NTN bearing is subjected to static and indeterminate axial additional load);
12. The clearance of the NTN bearing is too small, and the rotation is too tight (the tightening sleeve is too tight);
13. NTN bearing is noisy (caused by the end face of the roller or the ball is slipping);
14. The fit between the NTN bearing and the shaft is too loose (the diameter of the shaft is too small or the adapter sleeve is not tightened);
15. The shoulder is too large (touching the seal of the NTN bearing and rubbing);
16. The shoulder of the seat hole is too large (the seal of the NTN 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 (touching the NTN 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 pressure pit on the steel ball or roller (caused by hammering NTN bearing when installing);
21. NTN bearings are noisy (with external source interference);
22. The NTN bearing is discolored and deformed by heat (caused by the use of a spray gun to disassemble the NTN bearing);
23. The shaft is too thick to make the actual fit too tight (causing the NTN bearing temperature to be too high or noise);
24. NTN bearings are noisy (NTN bearings have fretting abrasion).
25. NTN bearing housing hole diameter is too large, the actual fit is too loose (NTN bearing temperature is too high - outer ring slip);
26. NTN bearing housing hole becomes larger (NTN bearing housing hole of non-ferrous metal is enlarged, or becomes larger due to thermal expansion);
27. The diameter of the seat hole is too small (causing the NTN bearing temperature to be too high).
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