Epistle on electric motor bearings part 1

[LHC]

bearings are fairly cheap. And there is the issue that unless you match the greases one can be completely incompatible with another basically making it useless. Then there's the fact that slightly pooched bearings will still seem really smooth at hand turning speeds.

imo its not worth not replacing them since you have it apart.

as for noise and the marks on the stator, a contamination of some sort now cleaned out? Set the lathe up between lathe centres. In theory there should be negligible runout at the bearings (rotate rotor not the bearing race) but if there is a bit note it and compare it to runout in the middle, that'll give a hint if its bent/warped enough to rub.

That's a great idea - thanks ! My lathe is too far apart to set up the rotor between centers - but - I can take it into my friend's place of work and do it there.

[Mcgyver]

looking at the pics again it seems the rotor was marked all the way around suggesting it is not bent or badly unbalanced...else the marks would be on one side. Are they similarly all the way around the stator? if so that would support the idea that something got in there

[Michael C]

A few years back my 10ee took to making a screeching noise everytime I went above 1500 rpm. Couldn't for the life of me figure it out. Then the motor had a wire break inside. Took the motor to shop and they fixed wire and replaced the *looks good* bearings. Noise gone even at 3000 rpms. I guess every 50,000 hours the bearings need replacing even if they look good. Funny part was guys at motor shop insisted that my DC motor wasn't original to lathe that it must have come from an elevator. I quit arguing with them and let them be right.

cheers
michael

[LHC]

looking at the pics again it seems the rotor was marked all the way around suggesting it is not bent or badly unbalanced...else the marks would be on one side. Are they similarly all the way around the stator? if so that would support the idea that something got in there

Yes, the stator is scuffed all the way around as well, so that would support the theory of debris. Still easy enough to check the rotor for warp though and will do that in a day or so for "completeness".

[LHC]

Well I have been jumping around on the lathe tear down and only today got back to checking the bearings on the armature. I put it between centers on a lathe at a friend's place of business, and used a mag base with a dial indicator. There's absolutely no movement on the needle as we rotated and pushed and prodded each bearing. These things are staying put on the shaft and I'm just going to wash them out and re-pack them when the motor goes back together.

Thanks once again for all the feedback and tips. The brake cleaner seems to be the only thing that will truely solubize this old grease, and using it on the end housings worked like a charm.

Cheers,
Lewis

[ogre]

This thread has been a huge educational trip to read from beginning to end. Thanks to all who said theyre piece!