on Screw Threads
Sir Joseph Whitworth proposed this
thread in 1841. This was the first standardised thread form.
The form of the thread is shown in the diagram. The principal
features of the British Standard Whitworth (BSW) thread form
are that the angle between the thread flanks is 55 degrees
and the thread has radii at both the roots and the crests
of the thread. The relevant standard for this thread form
is the British Standard BS 84 - 2007. The thread form is now
redundant and has been replaced by Unified and Metric threads
but there are many applications in which it is still used.
The British Standard Fine (BSF) thread has the same profile
as the BSW thread form but was used when a finer pitch was
required for a given diameter.
p = pitch of the thread
d = depth of the thread
r = radius at the top and bottom
of the threads
d = 0.640327 p
r = 0.137329 p
British Standard Brass (BSB) Threads
There are other threads that are based upon the Whitworth
thread form. British Standard Brass (for which there is no
British Standard) is based upon the Whitworth thread form
with all diameters having 26 threads per inch (tpi). It was
used on general brass work, gas fittings and brass tubing.
It is also reported that antenna bases should use this thread.
The specific dimensions for the thread can be derived by treating
it as a special Whitworth thread. The thread may have come
about as an attempt at standardisation by gas burner fitting
Model Engineers (ME) Threads
Established in 1912, the Model Engineers thread is based
upon the Whitworth thread form and was used in instrumentation
as well as by model makers. It was a fine pitch thread having
32, 40 or 60 (tpi).