BSF stands for British Standard Fine. It is a screw thread standard defined by the British Standards Institution (BSI). The BSF thread is a fine pitch thread that is complementary to the British Standard Whitworth (BSW), which is a coarse thread standard. Both of these were used extensively in Great Britain and the Commonwealth countries in a variety of applications before the metrication movement, which led to the adoption of the metric thread standards. The BSF thread has a finer thread pitch than BSW, which allows for more threads per inch, providing a finer adjustment and a tighter fastening.