In article ,
Keith Marshall wrote:
I've never tried one on a powdered coated panel but chassis or knockout
punches would probably give you much better results than a hole saw.
They're more expensive but it might be worth it. They give a really clean
hole.

Agreed, with the punch on the side towards the outside, and
the die towards the back of the panel, since it will probably scuff the
power-coat finish somewhat.

Here's one source:

http://www.mcmaster.com/

Type "knockout punches" into the search box.

*** Warning *** -- a 3" chassis punch and a 3" knockout punch
produce different sized holes. To be right on size, you want the
chassis punch, or at least to buy a knockout punch by the size of hole
it will produce, rather than the ID of the conduit which it is designed
to accept. At the price that these things go for, you *really* want to
be sure that you get the right one.

You'll also need a pretty hefty vise to hold the flats on the
punch, and (ideally) one of the ball-bearing drive screws. If you were
going to be making a lot of these, you might want to spring for a
hydraulic driver for the punch, too. But for your single panel, I don't
think so.

Hmm ... check whether your local tool rental shop has knockout
punch sets (they are not likely to have the chassis punch sets), so you
can measure to see what size is right -- and perhaps rent the punches
*with* the hydraulic driver. After all -- I believe that you said 1/8"
aluminum, and this is a bit thick for a knockout punch, even in
aluminum.

Good Luck,
DoN.

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