On Sep 4, 2:23*pm, Joe Pfeiffer wrote:
I need to make a total of 44 rectangular holes in some reasonably thin
aluminum. *22 of them have to be .56" x .52"; 22 have to be .81" x .52"

I had assumed I would be able to go down to harbor freight and buy a
rectangular chassis punch; no, the cheap generic punches are all round,
and the only rectangular punches I've seen are special-order for
hundreds of dollars.

So... *any good ideas (or sources of cheap rectangular punches!), or
should I plan on a day or so with my nibbler and a corner punch?
--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)

Drill round, nibble and file to mark. HF DOES carry a pneumatic file,
cheap at the half-off price. Where they nail you is with the file
sets. It does work, I've used it on several projects where the amount
of filing would be tedious. I have a square Greenlee punch, runs 1/2"
square, though, and worth a lot more than the $5 I paid from the odd-
tool closeout bin. Have never seen another except on paper and special
order at that.

Could also use a micro-die grinder with an appropriate burr to square
the hole a lot faster. Would leave less to file to square the corners
out. I've used a carbide burr on steel panels for expanding a knockout
for an off-center conduit, worked well, watch out for hot flying
chips. Another old dodge is to drill the corners with a really small
drill, then chew to that point with whatever and quit.

Stan