I have a little emergency project on the go - re-creating the locking wheel nut key I unknowingly lost a few weeks back and now need!. I've sorted out the design OK, but the only suitable material I have knocking around is some 25mm 304 stainless round bar, which is likely 50HRC absolute tops, probably less as I cut a billet off the rod with a hand hacksaw no probs. Now I have a couple of the above mentioned cutters which might do the job, but has anyone ever tried them on stainless, and if so what sort of DOC and feed worked best please?