Grinder nut problem.

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.

I would have to check the exact model I have at work but it looks identical, I’m not sure if mine has the e-clutch.  I’ve never tightened mine with anything other than my hand and I’ve never had the nut come off with daily use in a fab shop.  In the description it says tool free accessory change and it makes me wonder what they’re referring to.  I know in a demo video of the dewalt 60v grinder it says to release the nut you push the lock button as the tool is spinning, sounds crazy and I’ve never done it, but they also have a different nut design with a locking spring thing.  I would guess something isn’t working right and stopping the motor too fast causing the nut to come loose.