Whitworth taps and dies BSW BSWF

The Whitworth thread (named after the English engineer Joseph Whitworth who invented it), developed in 1833, is the first standard thread design and is still in use today. It has two pitches, fine and coarse; the thread has a 55° point angle.

The Whitworth thread is described in ISO 7 and ISO 228, referring to the British Standard Pipe, the thread used in Great Britain for water pipes.

Dimensions are based on the nominal outside diameter of the screw, similar to the ISO metric thread, but are expressed in inches and fractions of an inch; the thread pitch is expressed in threads per inch. Unless otherwise indicated, standard pitch is used.

Example: A 1 1/2" Whitworth thread is written as 1 1/2 W, meaning a standard pitch, which for this size is 6 threads per inch.

For different pitches or non-standard threads, the following is indicated: - the size in inches (without the _"_ sign) - the letter "x" - the number of threads per inch - the letter "W"

The Whitworth thread has a structural function (bolts), similar to its use in metric bolts.

In several English-speaking countries, the Whitworth thread has been abandoned in favor of metric: for example, the U.S. automotive industry has used metric bolts since 1970.