B.S.P.T.
British Standard Pipe Thread
British Standard Pipe 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 used:
Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP)
Taper threads, British Standard Pipe Taper thread (BSPT)
Just to confuse things, often the T in BSPT refers to Thread and doesn't indicate either Taper or Parallel.
The threadform follows the British Standard Whitworth standard
The table below shows dimensions for male threads.
|
Thread |
Threads per inch |
Pitch mm |
Outside Diameter mm |
Outside Diameter inches |
|
1/16 |
28 |
0.907 |
7.723 |
0.304 |
|
1/8 |
28 |
0.907 |
9.728 |
0.383 |
|
1/4 |
19 |
1.337 |
13.157 |
0.518 |
|
3/8 |
19 |
1.337 |
16.662 |
0.656 |
|
1/2 |
14 |
1.814 |
20.995 |
0.825 |
|
5/8 |
14 |
1.814 |
22.991 |
0.902 |
|
3/4 |
14 |
1.814 |
26.441 |
1.041 |
|
1 |
11 |
2.309 |
33.249 |
1.309 |
|
1.1/4" |
11 |
2.309 |
41.910 |
1.650 |
|
1.1/2" |
11 |
2.309 |
47.803 |
1.882 |
|
2 |
11 |
2.309 |
59.614 |
2.347 |
|
2.1/2" |
11 |
2.309 |
75.184 |
2.96 |
|
3 |
11 |
2.309 |
87.884 |
3.46 |
|
4 |
11 |
2.309 |
113.030 |
4.45 |
|
5 |
11 |
2.309 |
138.430 |
5.45 |
|
6 |
11 |
2.309 |
163.830 |
6.45 |
This is a 1/2" thread, you can count 14 threads in one inch.
An end view of a 1/2" male
thread
As the name of the sizing does not match the actual diameter, there can be some confusion over sizing. We have shown some pictures of two of the more popular sizes along side popular UK coins.
First, a half inch thread which is similar in size to a 1 penny coin.
Second, a three quarter
inch thread which is similar in size to a 2 pence coin :
Typical uses and sizes are :
1/4" Compressed air connections
3/8" Oil line connections
1/2" Basin and sink taps, radiator inlets, old outside tap outlets
5/8" Old outside tap
outlets (very rare)
3/4" Bath taps, washing machine inlet hose connections, modern outside tap outlets
1" Domestic heating boilers
1.1/4" Wash hand basin wastes (bathroom sink)
1.1/2" Sink wastes
(kitchen sink), bath wastes, WC syphon outlets
2" Modern WC
flushvalve outlets
A selection of "Black Iron" BSPT fittings :
A selection of plumbing fittings with BSP threads :
All reasonable steps have
been taken to ensure that information on this website is accurate,
but we do not warrant that such information is accurate or
complete.