Given a desired tap depth, is there a formula for the drill depth?
Along those lines, here is a ditty I use for tapping. R8, R9 establish the relationship between drill and tap depths in subroutine L200, and get passed to the Z's in the drill/tap cycle, preserving the relationship. This also minimizes the error of changing one, and not changing the other.
I have chosen a drill depth 50% greater than the tap depth. Normally, I would assign these numbers to V variables, and later pass those on to R variables, but with no real calculations, this isn't really necessary here.
Feel free to critique the tapping code, as I have no idea why shit is the way it is, just that it works.
N14#R8=.48' tap depth
N15#R9=1.5*R8' drill depth
N22( MAIN PROGRAM
N31M6T21( #21 DRILL