Grizzly G0935 Spindle Bearing Surprise

alright, stethoscope helped rule out the nose / ACB. so it was either the DGB on top or the pulley assembly. I let it run at 2k rpm for 10 minutes and checked temps. The nose was fine (100F), the top of the quill was cold, but the pulley was hot (140F).

How could that be the case? I didn't touch anything on the pulley assembly. I unfortunately have no way of knowing if it was bad before I pulled everything apart....but it certainly wasn't making any knocking noises like it is now.

I've also just finished running the pulley assembly only (spindle not installed) to see how it does. Knocking is mostly gone but it still gets pretty warm (100-120F). *MAYBE* my belt tension? It actually feels a little loose if anything (this machine isn't easy to tension well).

EDIT: to include that the spline fit from pulley to spindle is not great. lots of slop in pitch/roll. and it sure sounds like I can recreate the knocking by rattling that fit.
 
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When I heard the sound in your video, my first thought was the pulley area. Glad you ruled out the spindle bearings. There is a bearing in the pulley assembly, it’s possible that one might be going bad. When you get it all back together, see if the spline can be moved back and forth, that should be rigid. If that moves, it means something in your quill is allowing it to move and could be rattling around in the pulley sleeve. If the pulley bearing is bad, the sleeve could be what is rattling around. The pulley bearing should be relatively cheap since it doesn’t need to be precision. The manual says it’s an open bearing, but my mill has a shielded bearing in that position (different make/model), so you might want to go with a shielded or sealed bearing to keep any contamination out of it unless there are some seals that protect it.

For tensioning belts, you don’t need a lot for it to transmit power. If the belt gets over tensioned, it can fail that bearing quickly. The manual says a 1/4” deflection with moderate finger pressure, I love how they always make that so vague! Make sure you are getting some deflection of the belt and it’s not tensioned like a guitar string.
 
@Ischgl99 thanks. I thought I was starting to stray from the thread-topic so posted the spline / pulley question in the Q&A Forum. Will take the discussion there if you're fine with it.

That bearing is sealed on my assembly... which is another diff with the manual. It feels brand new. The spindle / splines are rock solid when I push on it.
 
It wouldn't be the hobby machinist forum if the thread didn't stray lol. I'll check in at the other thread.
 
Grizzly responded with:
We have found the correct replacement bearing and will still investigate the parts listing and correct any incorrect parts.
Click to expand...
And the replacement arrived today. They shipped a pair of angular contact bearings. How confusing. I get that these are typically installed in pairs but there's no way to do that on this spindle.

20240911_5924.jpg
 
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