26-12-2021, 01:25 PM
(24-12-2021, 12:23 PM)Parazine Wrote: I'm not sure how widely used BA threads were pre-war, they tended to become more common after the unified threads were introduced, post war, when 2BA and 4BA seemed to predominate.
As far as I know, 2BA & 4BA were used in the 1920s & 1930s for electrical equipment and for attaching instruments to metal dashboards.