I have a sheet metal (galvanized steel) box on my roof that's currently protecting the return and supply ducts for my old package unit air conditioner. I'm replacing it with a split system, and repurposing the steel box and original holes through the roof for the new refrigerant lines.
I bought a set of Sigrist exit seals to use for the horizontal penetrations of the new refrigerant lines through the wall of the box, but I have no idea how to actually go about CUTTING the 2-1/4" holes they require... the holes are way too big for a drill bit, and (AFAIK) hole saws are only for cutting through wood (and other relatively soft materials).