[Mr Bill]

Now, as far as punching is concerned, making a small punching block may be harder than you think. ... Issues I came across:
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2) Hanging chads are a real problem and they are hard to avoid without having to cut them off manually. Chads may be less of a problem with PET.
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3) Round holes did not work reliably in any (Pentax SLR) camera I tried. Lot's of problems with jamming. You need a rectangular hole but I don't think it needs to exactly match the ANSI spec. There is some tolerance.

I had no real machining tools to do this and was just working with a dremel tool, nails (with the point cut off and then modified with a v-notch in the face) for the pins and aluminum for the die. So, I am not saying it cannot be done, these were just some issues that I found.

Jason, thanks for the reality check. These are some of the issues I would expect. I think the solution to "hanging chads" is in extraordinary precision in the centering and clearance between punch and die. I'd guess that the speed of the punch is also a factor, as might be use of a high vacuum below the die set.

Re: round holes: I don't think these are at all desirable for film transport (in cameras, etc). But "round" makes it simpler for a home machine shop to make punch and die sets, and to have these precision-aligned (within reason). It wouldn't be necessary to have the rotational alignment near perfect, as it would be with rectangular punches.

I'm sure it can be done, I'm just saying the reality is a lot more difficult than it appears.