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Grinder nut problem.


M80

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I wanted to run this by you guys and see if anyone has run into this before.

 

We have a grinder at work. I believe it is [this](https://www.milwaukeetool.com/power-tools/corded/6146-30) Milwaukee. Every time you use it the nut loosens up. It happens with grinding wheels and cutting wheels and flap wheels. Doesn't matter what brand wheel. The nut is being used in the proper orientation. You can use the spanner wrench and crank the shit out of it. It doesn't matter how tight you get it, it loosens up every time. If seen the nut go flying off it after you release the trigger. We all have been using grinders daily for 15+ yrs. It is definitely a tool problem, not an operator problem. But it has me baffled. Anyone run across this?

 

I did search this on google and I did find someone else with the same problem on the weldingweb forums. 

http://weldingweb.com/archive/index.php/t-465161.html

They got a lot of suggestions, but no real solution.

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It sounds like you guys know how to use a grinder properly and that you have tried multiple ways to remedy the issue. If it were me I would contact Milwaukee and see if they can offer some help, or toss it out entirely. As you know flying grinder parts and wheels is not a good thing.

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Logically this makes no sense. The friction against the wheel should cause it to tighten on it's own with the spin of the shaft and against the material you're cutting. Even some insane vibration wouldn't explain this. I tighten my blades by snugging the nut, and grabbing the blade with my hand and using it to tighten the rest of the way. This has never failed. 

 

Let us know if you find out anything that explains this. 

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How quickly does it stop when you release the trigger?  If it feels like a braking grinder, grinding down whatever it's catching on and/or greasing the bearings should do the trick.

 

If you've ever hit the wheel lock on a grinder right after shutting it off, you'll notice the nut loosens and sometimes files off along with the wheel.  This is the principle for some tool free grinders because it loosens the nut, but those have a notch in the nut and spindle so it doesn't spin all the way off, just loosens.  I'm guessing the brake on the new milwaukee grinder is part of the reason it can use the tool-free nut, because if you've ever tried to remove a grinding wheel that's been worn down without changing you know that little twist handle won't cut it.  Slowing quickly isn't so much of a problem if it is smooth, but if the spindle or motor or anything is catching somewhere it acts sort of like an impact driver to loosen the nut.

 

That was a lot more rambling than I expected.

tldr: Slowing down reverses the force of speeding up and can loosen the nut instead of tightening it.

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How quickly does it stop when you release the trigger?  If it feels like a braking grinder, grinding down whatever it's catching on and/or greasing the bearings should do the trick.

 

If you've ever hit the wheel lock on a grinder right after shutting it off, you'll notice the nut loosens and sometimes files off along with the wheel.  This is the principle for some tool free grinders because it loosens the nut, but those have a notch in the nut and spindle so it doesn't spin all the way off, just loosens.  I'm guessing the brake on the new milwaukee grinder is part of the reason it can use the tool-free nut, because if you've ever tried to remove a grinding wheel that's been worn down without changing you know that little twist handle won't cut it.  Slowing quickly isn't so much of a problem if it is smooth, but if the spindle or motor or anything is catching somewhere it acts sort of like an impact driver to loosen the nut.

 

That was a lot more rambling than I expected.

tldr: Slowing down reverses the force of speeding up and can loosen the nut instead of tightening it.

 

I've had this problem before on one of our grinders. The spindle lock was malfunctioning and was catching the arbor as it slowed down. This caused the nut to loosen up. Listen to the tool as it slows down and see if you hear any scraping or other noises. 

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