I have an ancient drill guide which attaches semi permanently to the drill (my old Black and Decker). Since my 30 year old drill is slowly going bad, I need to move the drill guide. I cannot get the guide shaft off my drill. There is a hole in the middle of the shaft and I have tried putting in a hex key and striking it sharply with a hammer. No joy. Any ideas other than to hit it harder? [attachimg=1]