British standard pipe thread
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.
Contents |
[edit] Types
Two types of threads are distinguished:
- Parallel ('straight') threads, British Standard Pipe Parallel thread (BSPP; originally also known as[1] British Standard Pipe Fitting thread/BSPF and British Standard Pipe Mechanical thread/BSPM), which have a constant diameter; denoted by the letter G.
- Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread; denoted by the letter R.
These can be combined into two types of joints:
- Jointing threads: These are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (In Europe, taper female 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 (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut.
[edit] Thread form
- the threadform follows the British Standard Whitworth standard
- 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 ending tangentially with the flanks
- the theoretical depth of the thread is therefore 0.64 times the nominal pitch
[edit] Pipe thread sizes
A list of 16 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 of a steel tube for which the thread was intended, but in the modern metric version of the standard, it is simply a size number.
Dash thread size |
Thread size |
Threads / in |
Pitch (mm) |
Thread major diameter |
A/F (mm) | Gauge length (mm) |
Corresponding pipe | Tapping drill size (mm) |
||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
(mm) | (in) | DN | OD (mm) |
OD (in) |
Thickness (mm) |
BSP.PL (Rp) | BSP.F (G) | |||||||
0.0625 | 28 | 0.907 | 7.723 | 0.304 | 4 | 6.60 | 6.80 | |||||||
−2 | 0.125 | 28 | 0.907 | 9.728 | 0.383 | 15 | 4 | 6 | 10.2 | 0.40 | 2 | 8.60 | 8.80 | |
−4 | 0.25 | 19 | 1.337 | 13.157 | 0.518 | 19 | 6 | 8 | 13.5 | 0.53 | 2.3 | 11.50 | 11.80 | |
−6 | 0.375 | 19 | 1.337 | 16.662 | 0.656 | 22/23 | 6.4 | 10 | 17.2 | 0.68 | 2.3 | 15.00 | 15.25 | |
−8 | 0.5 | 14 | 1.814 | 20.955 | 0.825 | 27 | 8.2 | 15 | 21.3 | 0.84 | 2.6 | 18.75 | 19.00 | |
−10 | 0.625 | 14 | 1.814 | 22.911 | 0.902 | 16 | 2.6 | - | 21.00 | |||||
−12 | 0.75 | 14 | 1.814 | 26.441 | 1.041 | 32 | 9.5 | 20 | 26.9 | 1.06 | 2.6 | 24.25 | 24.50 | |
−16 | 1 | 11 | 2.309 | 33.249 | 1.309 | 43 | 10.4 | 25 | 33.7 | 1.33 | 3.2 | 30.40 | 30.75 | |
−20 | 1.25 | 11 | 2.309 | 41.910 | 1.650 | 53 | 12.7 | 32 | 42.4 | 1.67 | 3.2 | 39.00 | 39.50 | |
−24 | 1.5 | 11 | 2.309 | 47.803 | 1.882 | 57 | 12.7 | 40 | 48.3 | 1.90 | 3.2 | 45.00 | 45.00 | |
−32 | 2 | 11 | 2.309 | 59.614 | 2.347 | 70 | 15.9 | 50 | 60.3 | 2.37 | 3.6 | 56.75 | 57.00 | |
2.5 | 11 | 2.309 | 75.184 | 2.960 | 17.5 | 65 | 76.1 | 3.00 | 3.6 | |||||
3 | 11 | 2.309 | 87.884 | 3.460 | 20.6 | 80 | 88.9 | 3.50 | 4 | |||||
4 | 11 | 2.309 | 113.030 | 4.450 | 25.5 | 100 | 114.3 | 4.50 | 4.5 | |||||
5 | 11 | 2.309 | 138.430 | 5.450 | 28.6 | 125 | 139.7 | 5.50 | 5 | |||||
6 | 11 | 2.309 | 163.830 | 6.450 | 28.6 | 150 | 165.1 | 6.50 | 5 |
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 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.
[edit] 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 7/1)
- Rc = internal taper (ISO 7)
- Rs = external parallel
- the thread size
Threads are normally right-hand. For left-hand threads, the letters "LH" are appended.
Example: Pipe thread EN 10226 Rp 2½
The terminology for the use of G and R originated from Germany (G for gas, as it was originally designed for use on gas pipes; R for rohr (meaning pipe).)
[edit] See also
[edit] References
[edit] External links
- Newman Tools Inc. and J.W. WINCO, INC. show the Whitworth form BSP or ISO pipe thread.