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Received a relatively old black and decker bench grinder from a relative. It works, mostly. About 50% of the time it powers up but doesn't spin - hand cranking gets it going, whether it starts fine or not it makes a dreadful racket for the first 10-20 sec. of operation. WD40 helps. Also, it seems like the wheels are off-center, ie they seem to not move in a perfect circle.

Is the situation with the slow start likely to result in imminent failure of the unit?

Is the situation with the uncentered wheels likely to result in damage to work?

Can any of this be fixed with some preexisting mechanical aptitude?

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  • I don't know much about the innards of bench grinders, but the folks over on GarageJournal do... garagejournal.com/forum/…
    – RQDQ
    Dec 24, 2011 at 22:30
  • Personally, I'd get rid of it. I recently read, maybe here, about someone who had a wheel crack and they got banged up pretty bad. That sort of vibration can't be good for wheel integrity at high RPM, and bench grinders just aren't that expensive.
    – pboin
    Dec 26, 2011 at 15:12
  • @pboin: Grinding aluminum can cause the wheels to crack. The wheel will load up with aluminum, which can expand and cause internal stresses. Then the wheel will eventually crack and send pieces flying everywhere.
    – Doresoom
    Jan 3, 2012 at 17:59

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If the wheels are wobbling, that could be either a symptom or cause of other problems. A symptom, if the wheel is wobbling because a bearing is bad or because the wheel has been damaged. A cause, if an unbalanced wheel caused excessive wear on a bearing.

As far as affecting the work goes, the answer is yes. There's no way to put a straight face on a wheel that's moving in an arc.

As for fixing it: if the problem is a damaged wheel, then you could replace them. But if the problem is a damaged shaft/bearing, then it's pretty much shot, and the new wheels would be wasted money.

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