get bimetal hole saws, you can get a dewalt or lenox kit for less than the price of two punches, and the hole saw kit will be much more useful in the long run
I used an 1 1/4 step bit to make element holes. I had to punch two holes in kegs and two in cover plates. 12 bucks on amazon. And I was able to use it for the sight glass holes and weldless valves.