All great ideas but I have to be quite accurate with the holes, after marking them out then drilling chances are they won’t be that accurate. The PCB has about 5 mounted parts that need to go through the holes on different sides and there’s no play. Plus they have to be neat. So that’s why Im thinking of making a template I can slip over the edge of the tin box, sort of an inverted U shape and then using a hardened bolt that’s been cut down with a cutting edge done on a lathe that then screws through the die and punches out the holes.