You also need to remember thread angles
The Unified series has a thread angle of 60 degrees
BSW, BSF and BSB have a thread angle of 55 degrees apart from BSC which has a 60 degree thread angle.
Personally I wouldn't use UNC fasteners on Whitworth threads but that's just me
Arwyn
I would agree given the choice but as they share the same tpi and given manufacturing tolerances using one with the other is possible in a non critical situation. There is one frustrating exception though ½" BSW is 12 tpi whilst ½" UNC is 13 tpi
