I found that with the hardware store wad punches, they seem to work the best, and keep their edges longer if they are chucked into a drill press, and then turned at the very lowest speed you can get on the press, while you " drill " the punch through a stack of felt, or cardboard, or fabric. If you use a hammer to hit the punches, the edges eventually curl on you, and you have to stop to grind or file them sharp again. If the punch is spinning in the drill press, you can easily touch up the edge of the punch with a stone or file so that it remains square to the shaft.