If you have an "NMB bearings" fan with noisy bearings, and dont wanna replace it, you can repack the bearings with new grease by doing these simple steps:

EDIT:NOW WITH PICS, and a few more in depth steps.

1. Peel back label on back of motor

2. VERY VERY carefully remove the plastic snap ring inside of the fan, be careful and cover it with your thumb coz they LOVE to fly!

3. store it in a VERY safe place so it dosnt get lost.

4. remove fan blade assembly from fan frame

5. remove bearings from fan's frame

6. look at the bearings, make sure they are relubeable(unsealed ball bearings) if unsealed, continue to step 6. if sealed, find a DEAD fan with good bearings and simply replace the ball bearings.

7. if it doesnt have sealed bearings, some dont, you can take the ball ina bearings out and soak them in rubbing alcohol(91 percent kind) to remove the old, spent grease.

8. dry them compleately to not let them rust from the small amount of water in the rubbing alcohol.

9. find some lightweight grease(even vaseline works) and re pack the freshly cleaned bearings with brand new grease, be sure the whole bearing is fully packed with new grease, or itll still make noise.

10. reassemble the fan and test. if it makes noise still, either the bearings are shot, or they arent packed enough. if they arent packed enough, pack some more light weight grease into them, and reassemble again. 

11. your fan is now refurbished and ready for work again! Ive done it to a few NMB fans. it works great if done properly! I hope I help some people with noisy fans, happy refurbishing of fans!

Bearings are essential to the machines you utilize everyday, for without having them, we would have to frequently replace broken machine components due to the and tear of friction. A bearing is a tool always reduce the friction which happens in machines. Friction is a a kind of energy that opposes the movement of a surface in moving or perhaps moving motion over an additional surface alongside which it is within contact. fag Bearings bear the frictional force and that is set up by the moving texture of the machine component.