"Colbyt" wrote:
-snip-

So what I want is a clean way to cut the duct without destroying the metal
on either side of the cut. As an example: much like cutting the four sides
of a wood box with a table saw.


I'd go with bob's method- but use a Dremel and [many] disks instead of
the angle grinder. I always feel like I have more control with the
Dremel.

Jim