I've got the Woodward version, does great on 20ga steel. Might do ok on 18ga but I've never tried it, no reason to! If you place the beads in the right place and flange the edges for a flush fit or just a stepped look for panels the 20ga. THINKS it's become 18ga. Does a good job on aluminum too, used it for aluminum panels up to .040 and no complaints. It will probably be replaced with a Mitler electric bead roller eventually, but for now and for what I paid for it I have no complaints!