You probably can't prevent injury, but knowing to kill the motor or push in the clutch would lessen the damage. I guess next time he will grab his hand type post hole diggers and sue when his hands get blisters. 1 has to understand there are dangers associated with using equipment. If you safety a piece of equipment where you can't get injured, it won't be worth using or the safety device will be removed and the manufacture will still be sued . It's a no win for the manufacture. Like I said in my previous post. 1 day we'll have to return to the stone age equipment because all the manufactures will be sued out of business. I injured my hand today when my Makita drill slipped off the screw and jammed into my hand causing my hand to be cut.. It sure is real sore as I type this...They should have a safety device built onto drill to prevent this..... Who do I sue ?? Makita, the screw maker, or the company that made the adapter to go in the drill chuck that allows you to drive the screw into wood,steel,etc, or to be on the safe side I'll just sue them all !!