Problem with Bench Grinder

[TheClaw]

I've got a pretty heavy duty buffer/grinder mounted on what used to be an old cargo grate (found under a porch ,guessing it's pretty old, but solid as a house). The other day, the door of the cabinet was open as as the garage door went up it got hooked on it and before I could stop it, it fell over and the grinder took a blow on the shaft as it hit the concrete.

Now it has a slight rattle or rumble noise as it spins. It turns ok, but clearly something been pushed out of alingment. I gave it a whack with a hammer from the other end to seen it was simply a matter of smacking something back in place but the noise is still there.

Before I open it up, is it relatively straight forward to repair these? Maybe replace the bearings? Is there an internal adjustment I should be aware of?

Maybe I should just use until I fry it? I've had it for 14 or 15 years.

Any advice from you all would be helpful.

Thanks,
Jeff

 

[Gary S]

I'd disassemble it and inspect the shaft where the bearings sit. Depending on how it was made, it is possible that a hit on one end could have moved the armature enough on the bearings to allow it to make contact with the housing.
If you see a shiny spot on one side of the bearings, it could indicate that the shaft got knocked sideways. If so, fix it. the bearings are likely OK. You can determine that when you get inside.

 

[Davefr]

As long as the shaft is still true then I bet the two end caps just got out of alignment with the stator. (I doubt this damaged the bearings).

Loosen both end caps and adjust them to where there is no rubbing between the rotor and the stator. (The air gap should be consistent between stator and rotor.)

 

[DARK AGE 53]

Have you tried running it without the wheels on it, might be the grinding or wire wheel that's the problem.

 

[mitusa]

Check runout on end of shaft....if it is bent it will cause a rumble.

 

[A_Pmech]

I would suggest starting by removing the grinding wheel from your buffer and putting it on a grinder with guards. The purpose of the guard is not primarily to prevent you from accidentally contacting the wheel, but to contain a wheel explosion. If the wheel hit the ground when the grinder fell over, the wheel should be trashed anyway.

As mentioned, check the runout on the shaft end which hit the floor. If runout is present in excess of .005" or so you'll have to straighten the shaft or selectively assemble the grinding wheel to negate the balance issue. Once dressed the runout won't be present on the wheel periphery.

If runout checks out OK or is random, the bearings are likely brinelled and that's the cause of the rumble. They'll have to be replaced, which is a very easy job. Just remove the end bells and tap out the old bearings. Be sure to keep track of any wave washers and put them back how they came out.

 

[Kevin54]

Ouch!!!! A Dayton motor. Not cheap.

Pull the grinding wheel and the wire wheel off of it and turn it on. If it still rattles, it's the motor. If it doesn't rattle, you busted the grinding wheel. You can "ring in" the grinding wheel by hanging it off of a round bladed screwdriver and tapping it on the side. If it rings, it's good. If it sounds like a dull sound, it's more than likely cracked.

Also, when turning it on with no wheels on it, watch the shafts to see if they are running straight or if they have a slight wobble. If any wobble at all, a wheel mounted on it will only magnify it some. Hopefully you only cracked a wheel and threw it out of balance.

 

[TheClaw]

I'll take off the wheels. I hit pretty straight on the side with the wire wheel (left side of picture) with not much of an angle. So it was largely a blow along the axis of the shaft.

All good advice. I'll let you know.

Thanks very much,
Jeff

 

[bighouse01]

That's a buffer (extended shafts), meant to hold fabric style wheels that do not explode like a grinding wheel(stone).

That could get dangerous. When a grinding wheel goes you don't see it happen. Just boom and its everywhere.

 

[TheClaw]

Thanks for all of the input. I took off the grinding stone and wire wheel. Still made the noise. Visually, didn't see much runout. Like I said, it took a shot straight on, not at an angle.

So I took the end caps off and slid out the shaft.


I didn't see much evidence of any rubbing.

This insides looked good too.

The left hand bearing spun ok. The right hand one made a little noise when spun by hand.

I'm guessing the right hand bearing is got a limited life right now. When I bought this I had a big polishing job to do. Nowadays I use it for small projects and rarely have it running for a long period of time. I think I'll let it go for a while and see what happens.

Thanks for all of the advise.

Jeff

 

[A_Pmech]

Might as well replace the bearings while you have it apart, they're only about $10 a piece more or less.

 

[TheClaw]

That's a buffer (extended shafts), meant to hold fabric style wheels that do not explode like a grinding wheel(stone).

That could get dangerous. When a grinding wheel goes you don't see it happen. Just boom and its everywhere.

Point taken. I don't buff with it much anymore. As you and a couple of the others guys suggested, a guard would be smart.

Thanks.