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

British Standard Whitworth British Standard Whitworth (BSW) is a screw thread standard that uses imperial-unit, imperial (inch-based) units. It was devised and specified by British engineerJoseph Whitworth in 1841, making it the world’s first national screw thread stand ...

(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 Metric or metrical may refer to: Measuring * Metric system, an internationally adopted decimal system of measurement * An adjective indicating relation to measurement in general, or a noun describing a specific type of measurement Mathematics ...

, standards. For highly stressed conditions, especially in motorcycles, a finer thread, British Standard Cycle (BSC), was used as well. BSF was developed by R. E. B. Crompton, and his assistant George Field. BSF threads use the 55 degree Whitworth thread form. It was introduced by the British Engineering Standards Association in 1908.Sidders 1969, p.16 The table provides BSF sizes, the

threads per inch A screw thread is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a ''straight'' thread and th ...

and spanner jaw sizes. The BSC column indicates where BSF and BSC threads match. The table shows suitable tapping drill sizes. Uncommon sizes are shown in italics.

Table

References

Bibliography

External links

*
Jaw sizes for sockets and spanners/wrenches

{{DEFAULTSORT:British Standard Fine Thread Thread standards Screws 1908 introductions Standards of the United Kingdom