Quote Originally Posted by Eric Danstrom View Post
That Makita router isn't designed for fault tolerance, it's call FMEA or failure mode effects analysis. We can be grateful those Makita engineers don't work in the appliance or automotive industries. The just of Design FMEA is to assure a single point failure can't allow the device to fall in a dangerous mode. In the OP's example something has failed intermittently and the result is the router runs full speed without any input from the user. A recent example of a bad design relying on a single sensor for critical data with no backup mode is the 737MAX.

I'm sure Makita has seen this failure already, I'd give them a call a listen to their reaction. I might contact the CPSC and see if they want to investigate. If there's a UL listing I'd contact them too.
We need to keep in mind that any device can fail, and protect ourselves by only using components (in the case of a router, bits) that can survive failure of the equipment being used (within reason anyway) when it fails in the full speed mode.

It would be prudent to only put in a router things that can withstand the maximum speed the router can attain.

Besides high speeds caused by speed control failure, there is always the potential for high speeds due to operator error. At least in my case (whoops! I forgot to turn the speed down!)...can't speak for others. In either case the result could be the same.

I would be willing to bet most router manufacturers have seen this same failure mode at least once. But don't think that is the root issue. The message in this thread is that router speed controls can and will fail full on. So don't put anything in your router chuck that cannot withstand the maximum speed the router can turn. (Or in any other tool for that matter).