Likely the reason why it seems quieter is because it doesn't have something solid to resonate off of. Like a guitar or a piano, strings alone don't make much sound. It's the resonation that occurs in the chamber of the guitar or the sounding board of the piano. Without mass to resonate off of it will sound quieter. When in the Hi-Fi it's louder because the metal frame amplifies (resonates) the sound.

Sounds logical,while it may cause a false conclusion if one is not aware of that.

No need to open the bearing just to lubricate it. They are not sealed so very well, so a drop or two of oil will penetrate after a few minutes. OR, put the whole bearing, by itself, submerged in a spoon ful of hot lubricating oil and let it cool. As it cools the air inside will shrink and pull in a bit of oil. That is a trick to oil those really small sealed bearings. They are not air-tight.

I am going to buy a new bearing anyway,since i reached to the red line of time that i let myself spend on this failure.but your second trick,to submerged all the bearing in hot oil seems as a clever idea that i will definitely try in the future.
Thanks.

 

No need to open the bearing just to lubricate it. They are not sealed so very well, so a drop or two of oil will penetrate after a few minutes. OR, put the whole bearing, by itself, submerged in a spoon ful of hot lubricating oil and let it cool. As it cools the air inside will shrink and pull in a bit of oil. That is a trick to oil those really small sealed bearings. They are not air-tight.

Something that i wonder about your second technique(submerge the bearing in hot oil).How hot should the oil be?50C-60C degree?
Won't heating the oil degrade the oil(breaks it down)?

 

Certainly "hot" is a relative term, and in this context I mean that it should be perhaps 20 to 30 degrees warmer than the bearing's temperature at the time.
As for the oil suffering breakdown because of the temperature increase, consider that the increase is not that great nor is it for an extended period of time. Besides that, the temperature should always remain within the safe handling range. I am not talking about boiling oil for hours, really. The higher temperature needs only to heat the bearing enough to cause the air inside to expand and some air pressure to cause a few bubbles. Then the cooling down will create a vacuum inside and pull in some of the oil.
So really, if the oil is only as hot as hot coffee that is hot enough. The big point is that the bearing remain submerged as the oil cools, so that some is drawn inside the seals.

 

Certainly "hot" is a relative term, and in this context I mean that it should be perhaps 20 to 30 degrees warmer than the bearing's temperature at the time.
As for the oil suffering breakdown because of the temperature increase, consider that the increase is not that great nor is it for an extended period of time. Besides that, the temperature should always remain within the safe handling range. I am not talking about boiling oil for hours, really. The higher temperature needs only to heat the bearing enough to cause the air inside to expand and some air pressure to cause a few bubbles. Then the cooling down will create a vacuum inside and pull in some of the oil.
So really, if the oil is only as hot as hot coffee that is hot enough. The big point is that the bearing remain submerged as the oil cools, so that some is drawn inside the seals.

Okay,great,i got the idea.
According to physics,your method seems to guarantee the lubrication of the bearing more than just drop an oil on it.
Thanks again.

 

The heating trick is a "cheating trick" that I learned from an associate who was at least twice my age. They pointed out that there was no way I could drill a hole to lubricate inside a small gearbox without getting chips into the small gears inside. Totally correct it was. AND the best part about the hot oil dip trick is it can be repeated to provide more oil if the first drop was not enough.