[JesseK]

Side topic -- somewhat related I suppose --

For a 1-1/8" (or 1-1/16") Silver & Demming bit that would cut into 1/4" Polycarb and/or 1/4" Aluminum ...

... would we want to get a carbide-tipped bit or would a HSS bit suffice? This assumes that S&D bits can do the 1-1/8" hole without too much slop, which also assumes we would do starter holes with a smaller drill bit first. It would also be done on a mill we've been able to get within 1/64" after nominal practice.