Yeah, making my own punch and die is unlikely to succeed so, ebay to the rescue. Just ordered this ($10 on ebay): STRIPPIT PUNCH & DIE DOUBLE "D" .322'' X .377'' +.012'' 166S. This punch and die size should work for the BNC jacks I have. Will need a hand operated press setup. In looking at the cases I want to modify, they are all open in the back (no obstructions directly behind the places I want to punch holes, so I can mount the die on a piece of round stock and use a hand operated press. The hole size is pretty small so I should not need a huge amount of force and I think a hand operated press should work fine. We shall see.