I am posting this as a public safety announcement.
I am not looking for a discussion on my practices.

So i have used my Makita router for internal and external grinding.
The router has electronic speed control from 8000, -24,000 adjustable by a graduated wheel.
I have done ID grinding with the small grinding wheels 1/2" - 1" dia max rated rpm 30,000 with with speed dial set to full speed 24,000rpm.
And i have done some external grinding with a large 4" diameter wheel with the speed dial set at 8000 rpm.

I haven't used it for some time (many months)
I went to use it the other day and got injured quite seriously.

I had the dial set to 8000 for the larger wheel, turned the router on to let it warm up for a few seconds before using it, it was running fine for a while, i turned away to get something and the router ramped up to full speed for no apparent reason, the noise startled me and i turned around just as the wheel exploded. I didn't have any time to do anything, i got hit in the face with a piece of grinding wheel.
It hit me on the left side of my nose, below the cheek bone, broke my palate and pushed a couple of teeth and the bone that holds them into my mouth, split open my face, cut up my tongue, and bled profusely, inside and outside my mouth. I have had the first emergency surgery to do the initial patchup to remove the chunks of grinding wheel that embedded inside my mouth and had my face sewn up. I have to go to another surgery to get my palette repaired and my teeth put back where they belong, when the swelling goes down. For now i eating through a straw.


So other than the normal safety procedures you may follow, the take away from this is;
1. Routers electronic control are not to be trusted.
2. The can and do randomly change the speed without warning.
3. Don't run anything in the router that is not rated for the full speed of the router.
4. Electronic controls can and do malfunction when operating under normal circumstances.

From the manufacturer:
Variable Speed Control Dial Enables User To Match The Speed To The Application And The Electronic Speed Control Maintains Constant Speed Under Load

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