Thread Sizes
BSPT & BSPP Threads
BSP is BRITISH STANDARD PIPE:
Also known as Whitworth 55° Thread Form
BSPT is BRITISH STANDARD PIPE TAPER:
Thread form per AS 1722.1, BS 21, ISO 7
BSPP is BRITISH STANDARD PIPE PARALLEL:
Thread form per AS 1722.2, ISO 228
BSPT male threads seal against threads of fixed BSPT female.
Contact is made on the flanks of the threads.
Use of a thread sealant is recommended for BSPT male to BSPT female connections.
Measure the BSPT male thread Outside Diameter (OD), and female thread Inside Diameter (ID) at the first full thread near the end of the fitting.
BSPT & BSPP Threads Dimensions
|
BSPT & BSPP SIZE |
PITCH |
BSPT MALE THREAD OD |
BSPT FEMALE THREAD ID |
BSPP MALE THREAD OD |
BSPP FEMALE |
||||
|
inch |
TPI |
mm |
inch |
inch |
inch |
mm |
inch |
mm |
inch |
|
1/8 |
28 |
9.5 |
0.37 |
0.38 |
0.38 |
8.4 |
0.33 |
8.6 |
0.34 |
|
1/4 |
19 |
12.8 |
0.50 |
0.51 |
0.51 |
11.2 |
0.44 |
11.9 |
0.47 |
|
3/8 |
19 |
16.3 |
0.64 |
0.65 |
0.65 |
14.7 |
0.59 |
15.2 |
0.60 |
|
1/2 |
14 |
20.4 |
0.80 |
0.82 |
0.82 |
18.3 |
0.72 |
19.1 |
0.75 |
|
5/8 |
14 |
22.5 |
0.89 |
0.90 |
0.90 |
20.6 |
0.81 |
20.8 |
0.82 |
|
3/4 |
14 |
25.9 |
1.02 |
1.04 |
1.04 |
23.9 |
0.94 |
24.6 |
0.97 |
|
1 |
11 |
32.6 |
1.28 |
1.30 |
1.30 |
29.7 |
1.17 |
30.7 |
1.21 |
|
1 1/4 |
11 |
41.1 |
1.62 |
1.64 |
1.64 |
38.6 |
1.52 |
39.4 |
1.55 |
|
1 1/2 |
11 |
47.0 |
1.85 |
1.88 |
1.88 |
44.5 |
1.75 |
45.5 |
1.79 |
|
2 |
11 |
58.6 |
2.31 |
2.34 |
2.34 |
56.4 |
2.22 |
57.4 |
2.26 |
|
2 1/2 |
11 |
74.1 |
2.92 |
2.95 |
2.95 |
71.9 |
2.83 |
72.6 |
2.86 |
|
3 – |
11 |
86.6 |
3.41 |
3.46 |
3.46 |
84.6 |
3.33 |
85.4 |
3.36 |
Thread size refers to the nominal bore of the pipe.
Subtract approx. 1/4″ (6mm) from thread diameter measurement for nominal pipe size.
Pitch is Threads Per Inch (TPI).
“Gas”, “R” & “G” also refer to BSP.
“Male Iron (Pipe)” may be BSP or NPT.
NPT & NPS Threads
NPT is NATIONAL PIPE TAPER (AMERICAN):
Thread form per ANSI/ASME B1.20.1
NPS is NATIONAL PIPE STRAIGHT (PARALLEL)
Thread form per ANSI/ASME B1.20.1
NPTF is NATIONAL PIPE TAPER FOR FUEL
Thread form per SAE J476
NPSM is NATIONAL PIPE STRAIGHT MECHANICAL
Thread form per ANSI/ASME B1.20.1
National Pipe threads are similar in function to BSP threads, but are not generally interchangeable.
NPTF threads (also known as Dryseal) are an improvement to NPT.
Controlled truncation of threads mean the metal-to-metal thread seal is at root and crest of threads, in addition to flanks of threads.
Use of thread sealant is recommended for NPT male and NPT female connection.
Male thread Outside Diameter (OD), and female thread Inside Diameter (ID) are measured at the first full thread near end of the fitting.
NPT Threads Dimensions
NPT
|
NPT THREAD |
PITCH |
MALE THREAD OD |
FEMALE |
||
|
inch |
TPI |
mm |
inch |
mm |
inch |
|
1/8 |
27 |
9.9 |
0.39 |
8.4 |
0.33 |
|
1/4 |
18 |
13.2 |
0.52 |
11.2 |
0.44 |
|
3/8 |
18 |
16.6 |
0.65 |
14.7 |
0.58 |
|
1/2 |
14 |
20.6 |
0.81 |
17.8 |
0.70 |
|
3/4 |
14 |
26.0 |
1.02 |
23.4 |
0.92 |
|
1 |
11.5 |
32.5 |
1.28 |
29.5 |
1.16 |
|
1 1/4 |
11.5 |
41.2 |
1.62 |
38.1 |
1.50 |
|
1 1/2 |
11.5 |
47.3 |
1.86 |
43.9 |
1.73 |
|
2 |
11.5 |
59.3 |
2.33 |
56.4 |
2.22 |
|
2 1/2 |
8 |
71.5 |
2.82 |
69.1 |
2.72 |
|
3 |
8 |
87.3 |
3.44 |
84.8 |
3.34 |
NPSM
|
NPSM THREAD |
PITCH |
FEMALE |
|
|
inch |
TPI |
mm |
inch |
|
1/8 |
27 |
8.6 |
0.34 |
|
1/4 |
18 |
11.9 |
0.47 |
|
3/8 |
18 |
15.0 |
0.59 |
|
1/2 |
14 |
19.1 |
0.75 |
|
3/4 |
14 |
24.6 |
0.97 |
|
1 |
11.5 |
30.5 |
1.20 |
|
1 1/4 |
11.5 |
39.4 |
1.55 |
|
1 1/2 |
11.5 |
45.5 |
1.79 |
|
2 |
11.5 |
57.4 |
2.26 |
|
2 1/2 |
8 |
68.8 |
2.71 |
|
3 |
8 |
84.6 |
3.33 |
Thread size refers to the nominal bore of the pipe.
Subtract approximately 1/4” (6 mm) from thread measurement for nominal pipe size.
Pitch is Threads Per Inch (TPI).