I save old 3/8 drive sockets (especially the Japanese ones you somehow end up with in your box (?) ) and I grind a sharp point around the edge on those to make various size hole punches. If you hold the socket against your grinding wheel and spin it you can make a pretty good, even edge around the circumferance.

The bigger the socket the bigger the hole, and if you insert an old extension into the socket you have a handle to hold onto while you hit it with a brass hammer. Those are also good for making holes in gasket material when you need to create your own gasket. Because sockets are usually of some form of hardened steel the sharp edge stays sharp pretty long.

Don