BSW Whitworth Regular Thread (GB)

The BSW thread is the British regular thread. Its significance in terms of prevalence and use in Great Britain can be compared to that of the metric ISO-regular thread in Germany. The measurements of the BSW thread are based on the designs of Joseph Whitworth, the “father of thread norms.” The British engineer designed the thread in 1841, and it was later included in the British Standards series in norm BS 84. This history is reflected in the full name of the thread; the abbreviation stands for British Standard Whitworth. Colloquially, it is still often simply referred to as the Whitworth thread. The BSW thread was the first nationwide thread norm in the world and is the basis for many other thread types that build on its geometry. Outside Great Britain, however, it is hardly used today.

The BSW thread is an inch thread with a 55° flank angle. The pitch is given in threads per inch.

For thread designation, the letter abbreviation is combined with the external diameter in inches. Both BSW and simply the letter W for Whitworth are used as abbreviations. Thus, the designation for the BSW thread is, for example, BSW 1/2" or W 1/2".

In the thread table for the BSW thread, the external diameter in inches and converted into mm is listed, as well as the pitch in threads per inch and also as a metric value. The core hole diameter for the BSW thread is also found in our table. This is needed if you want to cut a BSW thread and make a pilot hole for this purpose. Dies and taps for the BSW thread can be found via the links directly in our shop!