[Lynn Eades]

BSF is the fine thread as opposed to whitworth which is the coarse British thread. both have a 55 degree included angle.with a rounded valley, and flat crests, while UNC/UNF have a 60 degee included angle, with flat valleys and flat crests. Thats how I understnd it anyway.
On thread forms. A turned thread from a lathe etc, will not be as strong as a roll formed thread (which the originals probably were) because the "grain' in the metal is cut by the lathe tool, whereas the grain in the roll formed thread follows the profile of the thread.
I think many "British Motor Lorries" have used 7/8 BSF threaded wheelstuds.(often 10 stud)