Standard set of screw thread sizes used in pipe fittings "ISO 7" redirects here. For the 7-bit coded character set, see ISO/IEC 646.
British Standard Pipe (BSP) is a set of technical standards for screw threads that has been adopted internationally for interconnecting and sealing pipes and fittings by mating an external (male) thread with an internal (female) thread. It has been adopted as standard in plumbing and pipe fitting, except in North America, where NPT and related threads are used.
Types
[edit]BSPP fitting
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.
BSPT threads[2]
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.
Thread form
[edit]
The thread form 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 where r ≈ 0.1373P
The theoretical depth of the thread is therefore 0.6403 times the nominal pitch h ≈ 0.6403P
Pipe thread sizes
[edit]
At least 41 thread sizes have been defined, ranging from 1⁄16 to 18, although of these only 15 are included in ISO 7 and 24 in ISO 228.[3][4][5][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 contemporary pipes tend to use thinner walls to save material, and thus have an inner diameter larger than this nominal size. In the modern standard metric version, it is simply a size number, where listed diameter size is the major outer diameter of the external thread. For a taper thread, it is the diameter at the "gauge length" (plus/minus one thread pitch) from the small end of the thread. The taper is 1:16, meaning that for each 16 units of measurement increase in the distance from the end, the diameter increases by 1 unit of measurement.
G/Rsize
Threaddensity(TPI)
Threadpitch
Majordiameter
Minordiameter
Gaugelength
Tapping drill
R 95%
G 80%
(in)
(in−1)
(mm)
(in)
(mm)
(in)
(mm)
(in)
(mm)
(mm)
(mm)
1⁄16
28
0.907
0.3041
7.723
0.2583
6.561
5⁄32
4.0
6.6
6.8
1⁄8
28
0.907
0.3830
9.728
0.3372
8.566
5⁄32
4.0
8.6
8.8
1⁄4
19
1.337
0.5180
13.157
0.4506
11.445
0.2367
6.0
11.5
11.8
3⁄8
19
1.337
0.6560
16.662
0.5886
14.950
1⁄4
6.4
15.0
15.3
1⁄2
14
1.814
0.8250
20.955
0.7335
18.631
0.3214
8.2
18.7
19.1
5⁄8
14
1.814
0.9020
22.911
0.8105
20.587
0.3214
8.2
20.7
21.1
3⁄4
14
1.814
1.0410
26.441
0.9495
24.117
3⁄8
9.5
24.2
24.6
7⁄8
14
1.814
1.1890
30.201
1.0975
27.877
3⁄8
9.5
28.0
28.3
1
11
2.309
1.3090
33.249
1.1926
30.291
0.4091
10.4
30.4
30.9
1+1⁄8
11
2.309
1.4920
37.897
1.3756
34.939
0.4091
10.4
35.1
35.5
1+1⁄4
11
2.309
1.6500
41.910
1.5335
38.952
1⁄2
12.7
39.1
39.5
1+3⁄8
11
2.309
1.7450
44.323
1.6285
41.365
1⁄2
12.7
41.5
42.0
1+1⁄2
11
2.309
1.8820
47.803
1.7656
44.845
1⁄2
12.7
45.0
45.4
1+5⁄8
11
2.309
2.0820
52.883
1.9656
49.926
5⁄8
15.9
50.1
50.5
1+3⁄4
11
2.309
2.1160
53.746
1.9995
50.788
5⁄8
15.9
50.9
51.4
1+7⁄8
11
2.309
2.2440
56.998
2.1276
54.041
5⁄8
15.9
54.2
54.6
2
11
2.309
2.3470
59.614
2.2306
56.656
5⁄8
15.9
56.8
57.2
2+1⁄4
11
2.309
2.5870
65.710
2.4706
62.752
11⁄16
17.5
62.9
63.3
2+1⁄2
11
2.309
2.9600
75.184
2.8435
72.226
11⁄16
17.5
72.4
72.8
2+3⁄4
11
2.309
3.2100
81.534
3.0935
78.576
13⁄16
20.6
78.7
79.2
3
11
2.309
3.4600
87.884
3.3435
84.926
13⁄16
20.6
85.1
85.5
3+1⁄4
11
2.309
3.7000
93.980
3.5835
91.022
7⁄8
22.2
91.2
91.6
3+1⁄2
11
2.309
3.9500
100.330
3.8335
97.372
7⁄8
22.2
97.5
98.0
3+3⁄4
11
2.309
4.2000
106.680
4.0835
103.722
7⁄8
22.2
103.9
104.3
4
11
2.309
4.4500
113.030
4.3335
110.072
1
25.4
110.2
110.7
4+1⁄2
11
2.309
4.9500
125.730
4.8335
122.772
1
25.4
122.9
123.4
5
11
2.309
5.4500
138.430
5.3335
135.472
1+1⁄8
28.6
135.6
136.1
5+1⁄2
11
2.309
5.9500
151.130
5.8335
148.172
1+1⁄8
28.6
148.3
148.8
6
11
2.309
6.4500
163.830
6.3335
160.872
1+1⁄8
28.6
161.0
161.5
7
10
2.540
7.4500
189.230
7.3220
185.979
1+3⁄8
34.9
186.1
186.6
8
10
2.540
8.4500
214.630
8.3220
211.379
1+1⁄2
38.1
211.5
212.0
9
10
2.540
9.4500
240.030
9.3220
236.779
1+1⁄2
38.1
236.9
237.4
10
10
2.540
10.4500
265.430
10.3220
262.179
1+5⁄8
41.3
262.3
262.8
11
8
3.175
11.4500
290.830
11.2900
286.766
1+5⁄8
41.3
287.0
287.6
12
8
3.175
12.4500
316.230
12.2900
312.166
1+5⁄8
41.3
312.4
313.0
13
8
3.175
13.6800
347.472
13.5200
343.408
1+5⁄8
41.3
343.6
344.2
14
8
3.175
14.6800
372.872
14.5200
368.808
1+3⁄4
44.5
369.0
369.6
15
8
3.175
15.6800
398.272
15.5200
394.208
1+3⁄4
44.5
394.4
395.0
16
8
3.175
16.6800
423.672
16.5200
419.608
1+7⁄8
47.6
419.8
420.4
17
8
3.175
17.6800
449.072
17.5200
445.008
2
50.8
445.2
445.8
18
8
3.175
18.6800
474.472
18.5200
470.408
2
50.8
470.6
471.2
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 and 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 2+1⁄2
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.)
Pipe and fastener dimensions
[edit]
G / Rsize
Typ. nut sizes
Corresponding pipe
DN
OD
Wall
(in)
(mm)
(mm)
(mm)
(mm)
1⁄16
3
1⁄8
15
6
10.2
2
1⁄4
19
8
13.5
2.3
3⁄8
22 or 23
10
17.2
2.3
1⁄2
27
15
21.3
2.6
3⁄4
32
20
26.9
2.6
1
43
25
33.7
3.2
1+1⁄4
53
32
42.4
3.2
1+1⁄2
57
40
48.3
3.2
2
70
50
60.3
3.6
2+1⁄2
65
76.1
3.6
3
80
88.9
4
4
100
114.3
4.5
5
125
139.7
5
6
150
168.3
5
ISO 7 (Pressure Tight threads)
[edit]
The standard ISO 7 - Pipe threads where pressure-tight joints are made on the threads consists of the following parts:
ISO 7-1:1994 Dimensions, tolerances and designation
ISO 7-2:2000 Verification by means of limit gauges
ISO 228 (Non Pressure Tight Threads)
[edit]
The standard ISO 228 - Pipe threads where pressure-tight joints are not made on the threads consists of the following parts:
ISO 228-1:2000 Dimensions, tolerances and designation
ISO 228-2:1987 Verification by means of limit gauges
See also
[edit]
AN thread
British standard brass thread
British Standard Whitworth
Garden hose thread
National pipe thread
Panzergewinde
Thread angle
Threaded pipe
Preceded byISO 6
Lists of ISOsISO 7
Succeeded byISO 8
References
[edit]
^"BSPM = British Standard Pipe Mechanical". Retrieved 14 July 2016.
^"Pipe Thread Types and Designations" (PDF). Archived from the original (PDF) on 2013-10-07. Retrieved 2013-12-27.
^maryland metrics. "Maryland Metrics thread data charts". Archived from the original on 24 July 2018. Retrieved 14 July 2016.
^"RoyMech: Pipe Threads". Archived from the original on 22 July 2018. Retrieved 14 July 2016.
^"How to ID British (BSP) Threads" (PDF). Retrieved 20 November 2017.
^"BSP Thread data". www.practicalmachinist.com. 2 May 2012. Retrieved 2016-07-15.
External links
[edit]
British Standard Pipe Parallel Thread Dimensions
British Standard Pipe Taper Thread Dimensions Archived 2017-09-27 at the Wayback Machine
BSP Thread Charts and Diagrams, showing dimensions of tubing and fittings
ISO 7-1:1994
ISO 7-2:2000
ISO 228-1:2000
ISO 228-2:1987
Parallel pipe threads G
Parallel pipe threads PF
v
t
e
ISO standards by standard number
List of ISO standards – ISO romanizations – IEC standards
