28-12-2019, 01:15 PM
The same as you, I can't find anything on Whitworth but BA does have a relationship:-
They are unusual in that they were probably the most "scientific" design of screw, starting with 0BA at 6.0 mm diameter and 1.0 mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then rounded to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch
Source:-
https://en.wikipedia.org/wiki/British_As...ew_threads
They are unusual in that they were probably the most "scientific" design of screw, starting with 0BA at 6.0 mm diameter and 1.0 mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then rounded to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch
Source:-
https://en.wikipedia.org/wiki/British_As...ew_threads