BSF also is known as British Standard Fine screw thread. They are of the Whitworth form having a 55 degree included angle. These gages were created because Whitworth gages could be too coarse. This thread form is now more often used for replacement parts. BSF bolts hold many engine and gearbox parts in a Series One.
WESTport provides a complete line of BSF (British Standard Fine) Thread Plug Gages. They are available in sizes from 3/16 inch to 4 inches. Free Technical support is available from our core of engineers to assist you with any questions you may have.