British Standard Fine

British Standard Fine (BSF) is a screw thread form, as a fine-pitch alternative to British Standard Whitworth (BSW) thread.

It was used for steel bolts and nuts on and in much of Britain's machinery, including cars, prior to adoption of Unified, and later Metric, standards.

For highly stressed conditions, especially in motorcycles, a finer thread, British Standard Cycle (BSC), was used as well.

It was introduced by the British Engineering Standards Association in 1908.

The table shows suitable tapping drill sizes.