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[Erich]

Randy, it was WW2 rather than WW1 where the crossover from Whitworth form to SAE began to change. Military equipment which came to the UK didn't have any Whitworth form threads, so the mechanics had to have and understand SAE thread pitch. I think that BSP is used here in the US, but all other bits are Whitworth form. BA developed from the Thiry thread which is a watch making thread form from Switzerland. Tony's link to British Fasteners will get you most of what you need. I will note that they are short some things and I have had to go elsewhere. BA is fairly easy as model makers use it. BSF is getting harder to find.

Erich in Mukilteo