British Standard Brass or British Brass Thread is an
imperial unit
The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thr ...
based
screw thread
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 t ...
. It adopts the
Whitworth thread form with a pitch of 26
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 a thread angle of 55 degrees for all diameters.
It is often wrongly called ''British Standard Brass'' but is not actually covered by a
British Standard
British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under th ...
.
The reason for adopting 26 tpi, is brass tube has a relatively similar wall thickness irrespective of the outside diameter of the tube, therefore as BSW thread depths are determined by the threads per inch, a lower tpi would reduce the strength of the tube or cut right through it. Brass tube threads can be confused with the
British Standard Cycle British Standard Cycle (BSC or BSCy or CEI) is a British Imperial screw thread standard. Unlike other major British imperial thread standards (British Standard Whitworth and British Standard Fine) the thread runs at a 60 degrees rather than a 55 d ...
thread, one of which that is most common is also 26 tpi. The difference being the thread angle of the British Standard Cycle is the same as the metric thread angle of 60 degrees.
Nominal sizes are usually in the range to 2 inches.
See also
*
British Standard Pipe (BSP)
*
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 ...
*
National pipe thread
American National Standard Pipe Thread standards, often called national pipe thread standards for short, are United States national technical standards for screw threads used on threaded pipes and pipe fittings. They include both tapered and s ...
(NPT)
*
Unified Thread Standard
The Unified Thread Standard (UTS) defines a standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wi ...
(UTS, including UNC, UNF and UNEF)
References
{{Reflist
Thread standards
Screws
Standards of the United Kingdom