The British standard pipe thread (BSP thread) is a family of standard screw thread types that has been adopted internationally for interconnecting and sealing pipe ends by mating an external (male) with an internal (female) thread. Two types of threads are distinguished: Screw thread, used to convert torque into the linear force in the flood gate. ...

• Parallel threads, which have a constant diameter.
• Taper threads, whose diameter increases or decreases along the length of the thread.

They can be combined into two types of joints:

• Jointing threads: These are pipe threads for joints made pressure-tight by the mating of the threads. They always use a taper external thread, but can have either parallel or taper internal threads. (In Continental Europe, taper internal pipe threads are not commonly used.)
• Longscrew threads: These are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (gasket) on to the surface of the external thread by tightening a backnut against a socket.

For both the taper and the parallel pipe threads, the Whitworth thread form is used, which has the following characteristics: This article is about mechanical seals. ... British Standard Whitworth (BSW) is one of three imperial unit based screw thread standards which use the same bolt heads and nut sizes, the other two being British Standard Fine (BSF) and Cycle Engineers Institute (CEI). ...

• symmetrical V-thread in which the angle between the flanks is 55° (measured in an axial plane)
• one-sixth of this sharp V is truncated at the top and the bottom
• the threads are rounded equally at crests and roots by circular arcs that blend tangentially with the flanks
• the theoretical depth of the thread is therefore 0.640 327 times the nominal pitch

Pipe thread sizes

A list of 15 thread sizes are defined by the standards, ranging from 1/16 to 6. The size number was originally based on the inner diameter measured in inches (25.4 mm) of a steel tube for which the thread was intended, but is in the modern metric version of the standard simply a size number. Mid-19th century tool for converting between different standards of the inch An inch is an Imperial and U.S. customary unit of length. ...

The major diameter listed is the outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" from the small end of the thread. The taper is "1 to 16", meaning that for each 16 mm increase in the distance from the end, the diameter increases by 1 mm.

Pipe thread designations

These standard pipe threads are formally referred to by the following sequence of blocks:

• the words "Pipe thread",
• the document number of the standard (e.g., "ISO 7" or "EN 10226")
• the symbol for the pipe thread type:
  • G = external+internal parallel (ISO 228)
  • R = external taper (ISO 7)
  • Rp = internal parallel (ISO 7)
  • Rc = internal taper (ISO 7)
• the thread size

Threads are normally right-hand. For left-hand threads, the letters "LH" are appended.

Example: Pipe thread EN 10226 Rp 2 1/2

References

• International standard ISO 7-1: Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions, tolerances and designation. International Organization for Standardization, Geneva.
• BS EN 10226: Pipe threads where pressure tight joints are made on the threads. (The European version of ISO 7)
  • Part 1: Taper external threads and parallel internal threads — Dimensions, tolerances and designation.
  • Part 2: Taper external threads and taper internal threads — Dimensions, tolerances and designation.
• BS 21: Pipe threads for tubes and fittings where pressure-tight joints are made on the threads (metric dimensions). British Standards Institute, 1985. (Superseded by BS EN 10226:2004).
• International standard ISO 228-1: Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions, tolerances and designation.
• BS 2779: Specification for pipe threads for tubes and fittings where pressure-tight joints are not made on the threads (metric dimensions), 1986.

Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ... The International Organization for Standardization (ISO) is an international standard-setting body composed of representatives from national standards bodies. ... British Standards is the new name of the British Standards Institute and is part of BSI Group which also includes a testing organisation. ... Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ...

See also

• Threaded pipe
• National pipe thread

A threaded pipe plug; note that the threaded portion is slightly conical and so touches the calipers at only two points. ... Threaded pipe and elbow National pipe thread (NPT) is a U.S. standard for tapered threads used around the world to join pipe and fittings. ...

External links

• Newman Tools Inc. and J.W. WINCO, INC. show the Whitworth form BSP or ISO pipe thread.