Probably the most unsafe hole saw I have ever used. The mandrel enters the saw blade by turning the blade clockwise. Saw blade CUT clockwise during use. If you stop the drill, the saw blade will CONTINUE to spin AND WILL BE TURNED RIGHT OFF THE CUT, falling to the ground or your project. It hit my hand. Since the saw blade weighs about 2 1/2 pounds, it's not at all certain that it will spin and cut what it lands on. Do yourself a favor and spend the extra $20 on a cobalt hole saw or any other with LOCK. You end up doing it anyway.