The moral of all this discussion is to not throw away that can of British Fasteners we all have on the shelf somewhere . My last BSA , a B50, requires both SAE and Whitworth tools to work on. I think where they had leftover inventory of parts from the 250 and 441 models they used them up.

I often would replace thru bolted stuff with SAE just to save the Whitworth for a bike that had to have those threads.

Mr Mike