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Bench grinder won't work

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Forum topic by Knothead62 posted 634 days ago 1764 views 0 times favorited 7 replies Add to Favorites Watch
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Knothead62

2364 posts in 1593 days


634 days ago

Topic tags/keywords: question bench grinder belt sander wont start

My neighbor gave me a bench grinder/belt sander combo a while back. It is from Northern Tool and is no longer offered, according to their website. My problem- the motor hums but doesn’t start up. Even if I manually turn the wheel (carefully), it doesn’t start up. Any suggestions? Hopefully, it is something simple. Thanks to all LJers.


7 replies so far

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Dan Krager

1517 posts in 866 days


#1 posted 634 days ago

Suggest remove the belt so the motor is independent of the sander/grinder. Note the direction the motor should turn. Carefully wind a small rope or strong string around the motor shaft like a starter rope on a mower. DO NOT FASTEN THE END to the shaft, just wrap the cord upon itself so it binds on the shaft long enough for a pull start. Pull sharply on the rope and when the motor is spinning rapidly (and the cord is free of the shaft) turn on the power. If the motor catches and runs, then the starting capacitor is bad. Simple replacement.
If it doesn’t, replace the motor.
DanK

-- Dan Krager, Olney IL http://www.kragerwoodworking.weebly.com

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Knothead62

2364 posts in 1593 days


#2 posted 634 days ago

Thanks. Dan, I could probably replace the whole thing for what it would cost to repalce the motor. Bruce, will give it a try.

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Dan Krager

1517 posts in 866 days


#3 posted 634 days ago

Don’t give up on the motor until you know for sure it won’t run. Starting and running are two very different things to an electric motor.
I enjoy the challenge of salvage!
DanK

-- Dan Krager, Olney IL http://www.kragerwoodworking.weebly.com

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Knothead62

2364 posts in 1593 days


#4 posted 633 days ago

It won’t start or run, Dan. Will work on it tomorrow and use the suggestions given.

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RussellAP

2950 posts in 918 days


#5 posted 633 days ago

If you can see if it has a centrifugal switch, then check to make sure some gunk didn’t get caught in it. It could be stuck in run instead of resetting to start. Simply remove the switch and clean it up, clean the actuator as much as you can and reassemble and try it out. When the motor starts the switch should be retracted and when it starts spinning the actuator throws out and the switch goes to run.

-- A positive attitude will take you much further than positive thinking ever will.

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crank49

3373 posts in 1603 days


#6 posted 633 days ago

I have a nice 3/4 hp @8” bench grinder I like a lot, but the start capacitor in it went bad.
It would hum but would not run, kicked the breaker if I let it hum for about 15 seconds.

I could take a rubber backed sanding disk in my drill and hold it against the grinding wheel to spin it up, and if I could get it spinning fast enough before I switched on the grinder, the grinder would grab hold and run.

If you can duplicate this you either have a bad capacitor or as stated by Russell, a stuck switch. Neither of which is expensive to replace or fix.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

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Knothead62

2364 posts in 1593 days


#7 posted 629 days ago

Mystery solved! I thought would play around with the bench grinder and try some of the things suggested. I turned the stone and noticed that it didn’t spin freely. I moved the belt on the other end and noticed it was hard to turn.
So, I took off the cover and belt, hit the switch and it works! I’ll just have to adjust the tension on the belt.
Many thanks to all for their advice. We learn something new every day.

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