I knew id did not make sense from the get go. Ya see with metric standard threads. ( not the fine version or special stuff ) there is a simple formula to work out what drill ya need. At the 60 degree thread flank pitch. Ya just subtract the pitch of the thread from the outer diameter and ya got the drill size that will work to run a tap into. See them is things i can measure and work out. Number drills just don't make sense to me.

I like simple stuff like that.

You make perfect sense, but still no use for that metric system here!...Lol.