I've not used hole punches, ever, but, I've seen them used. I've used
5-flute reamers in the past, 5-flutes are supposed to not chatter, they do!
My most recent trick for 3/4" holes, which had to be perfect, as it was
someone else's equipment, was to use a small drill, about 3/16", then
larger, about 1/4", or 5/16", then I used some high quality countersink
bits, 3/8", 1/2", 5/8", and 3/4". The hole was flawless, no chattering,
and no bending of the metal.
They aren't drill bits, so can't be pushed through, I just use a little
pressure, and let them do the work. It takes a while, but the
countersink bits are easy to control, don't grab, a don't chatter, and
don't bend the metal, turn up the edges, or raise burs, so this is now
my go-to. If I need to get down into something to make, or open a hole,
I use a drill bit extension.
In one case, I could drill a 3/4" hole from the top of an item, but
could only get to within ~2 feet of the bottom side. I used a drill bit
extension, and a round stone, like a ball, to sit in the hole from
underneath, and smooth the edges.
Kurt
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