Bob,
I only use 1-72's & I use a 1/16" bit for the hole to be threaded & ream the hole that is not to be threaded with a # 49 . I countersink the button head screws with as 9/64" & flathead screws with a 1/4" spade bit . Hope that helps . Joe
I taper all of my tangs after heat treat . I hollow out the center part with a 4 " wheel & then taper on the platen , holding the blade with a magnet. I do it all with old Blaze or 3M 967'a ,60 grit, on Bader 3 , 1 3/4 hp .
Joe