What goes into rebuilding a bench grinder?

[Twilight Fenrir]

My local metal yard has a big pile of discount junk fairly regularly... Last time I was in, a JET 1HP bench grinder was in it. They tell me the motor is burnt out in it, but that's as specific of information as I've got, aside from the fact that the arbor still spins freely.

So, I'm curious... is it something that could theoretically be rebuilt for a pittance? I realize it can't be diagnosed and pinned down with as little information as that. But, in general, how repairable are bench grinders?

I'm guessing not very, shy of brushes and switches. Rewinding is probably expensive? But, I just don't know that much about them... I'm pretty mechanically inclined though.

Thanks

[oldgoaly]

if the winding is burnt, then you would need to replace the insulted copper wire that makes up the start and run windings, now it could just be a relay or capacitor.

[kxxr]

Operator error is by far the most common cause of problems, no matter the machine... and, it is the easiest thing to fix! I'm not saying it will be that simple in this case, but if you plugged it in and it ran, I would not fall over dead from shock. If it can be had for scrap price or for free, I bet you'd know a lot more about it after taking it apart than you do now. Plus, it would be fun to do ; )

[oldgoaly]

here is what a cheap Sears grinder looks like on the inside, unless yours is 3 ph it will be similar. 

[Twilight Fenrir]

Thanks for the feedback.

I checked out JET's website, and they've got an exploded diagram with list of parts, and prices... the only thing that's stupendously expensive is the stator/winding, at $200. Everything else is less than $60. I didn't ask what they wanted for it, but I will when swing by today. If I can get it for $20-ish, I'll take it.

Even if I can't fix it... I might have a use for it as-is... I could slap a pulley on either side, and use it as a jack-shaft for powering my 1890 30" bandsaw. :3

[johnsironsanctuary]

I have removed the fields, took off the center cover, pulled one end off, put a v belt on the rotor and powered it with another motor with the whole works mounted on a board. I have seen some that you can't expose the rotor.

[Nolatoolguy]

a few years ago when I knew nothing about electric motors I read every source I could on them. Any broken electric motor or bench grinder I could get I would take. I would tear them down to study them. If I could I would rebuild. I often wouldn't spend more then fifteen bucks on parts. If it required a part more then that I just tossed it in the shed. It was a good learning experience.

When I had my garage sale I had over 20 working motors I sold. Probably double that for non running ones.

[mikeswrenches]

I am like you...if it's cheap enough, buy it.  That is an expensive grinder when new.  Especially if it is a 1750 rpm 1hp motor.

  It would be pretty hard to burn the motor out on a bench grinder unless it was just totally abused.  It's probably as simple as a new cord, the on/off switch, or as someone else mentioned, the capacitor.

Good luck!

Mike

[Twilight Fenrir]

Well, I paid a little more for it than I would have liked... but I'll tear into it momentarily, and find out if I bought an expensive paperweight, or stole an expensive grinder :P

It buzzes loudly when I plug it in, and hit the switch o.o

[Twilight Fenrir]

BUAHAHAHAHAHAHAHA! IT WORKS! IT F*ING WORKS! XD


I don't know what I did... but I took it apart, put it back together again... and it works! XD $250 grinder for $40! Pretty good day!

[oldgoaly]

good chance the relay stuck open, when you took it apart it has started working again, if it was me I'd get a new relay and capacitor just make sure it lasts! manual here
http://www.cpojettools.com/jet-577102-jbg-8a--8-in--1-hp-industrial-bench-grinder/jetn577102,default,pd.html

[Papaw]

Makes it an  even better score!!!

[bill300d]

Congradulations! You've done good for 40. Did it come with a stand, if so even better.
If it acts up again give one of the wheels a spin it'll probably come to life.

bill

[Twilight Fenrir]

Congradulations! You've done good for 40. Did it come with a stand, if so even better.
If it acts up again give one of the wheels a spin it'll probably come to life.

bill

Nope, no stand... I made my own stand out of a 100+ year old hand pump water spigot I found in the woods :P

Haha, my antique Craftsman grinder acted that way... had to give it a bit of a spin to get it started. Was nice, because it went whatever way I spun it, so it was reversible!

[bill300d]

when it does that the problem is in the start side of the motor winding. Usually it's a loose connection somewhere or the cap going bad or the relay sticking. In your case if it keeps starting ok than probably a loose connection.

bill