Like Pete, I make punches from K&S brass tube. Some are fashioned so they cut on the ID and others on the OD. Which is used depends on whether you want the hole or the disc. It also increases the number of hole sizes you can punch. I use a small hobby hammer on them, punching into the end grain of a piece of hardwood. A block of lead works good for this purpose too. The cutting ends hold up better than expected. I cut plastic sheet up to .010”, decals, different tapes, sand paper, and even thin aluminum. Occasionally the end will need to be dressed.
I also have a couple made from hypodermic tube, one as small as .010”, for the holes in the leather strap holding the bonnet of a Jag XK120. I’ll replace some of the brass punches with hypo tube as I get more sizes. They will last longer than the brass, but are more difficult to form the cutting end.