As others have pointed out, it will fly off the drill if stopped abruptly. A longer shaft with a lock nut gives this product 5 stars. You have to be careful because the thread is too short for the lock nut. I drilled my holes by laying plywood on top of a thicker board so that A) I could drill the holes safely and not overhead, B) the drill bit didn't go through the bottom board into the ground, and C) the bottom board faced the hole saw detaching and flying away (in most cases). I figured it would be best to get the drill up to speed before plunging the hole saw into the wood. Otherwise, it will connect poorly and hurt hands and arms. I was able to drill all 21 ceiling light holes plus a few practice holes with no problems other than those mentioned here.