On a bridleless lock,it would seem to me that the plate should be at LEAST.187
thick and the tumbler axle should fit to within .0005 and both plate and tumbler
hardened to about 60Rc for it to work and last any length of time.
I,ve never made one and no plans to do so but if I were,I'd use the formula above.
A frizzen pivot screw should have the smooth section of the shank in the lock plate
as far as possible.Three or four fine threads will hold it in place and make a fairly rigid
pivot point for the frizzen to turn on.
Bob Roller