Researching the issue... I see some ways to drill a square hole in
aluminum for hundreds of dollars.

Seems to me an inexpensive do-it-yourself way to do this slowly would be
to place a stencil pattern square over the material and then use a drill
or rotary tool with the cutting surface of the bit below the pattern.
And just move the tool around until it hacks the hole square. It might
be accurate enough if done carefully. But the rotary tool needs to be
held perpendicular while being moved around. I guess it could be done on
a rotary/router type table, while moving the material instead of the
cutting tool.

Any keywords for that sort of thing?

Thanks.



I wrote:

I need to cut a 1/2" square through 1/4" aluminum. It doesn't have to
be centered, but the dimensions of the hole need to be correct.

I'd like to use a router type tool that I made, but the aluminum would
have to be perfectly square.

Any tricky way to do that?

Thanks.