Question: is bsf the same as whitworth?
Answer: Whitworth thread is coarser than a BSF of the same diameter,but the same spanners are used on both ranges,and are often marked with both Whitworth and BSF sizes . A whitworth spanner or socket is larger than one marked with the same size in BSF for example a 1/4 inch whit is the same physical size as a 5/16inch BSF.