Fittings NPT versus BSPT Thread Sizing Charts
Fittings NPT versus BSP Thread Sizing Charts
BSP
BSP thread form stands for British Standard Pipe and is common in Australia and the commonwealth countries. It is based on trade size rather than actual diameter which can lead to some confusion when measuring ports.
There are two types of BSP threads;
- Parrallel (BSPP) - also known as G or Rp
- Tapered (BSPT) - also know as R or Rc
Both threads have the same pitch, angle (55 degrees) and shape (rounded peaks and valleys).
The below table gives the major and minor diameter for each BSP Trade Thread Size.
| Trade Size |
Threads per inch |
Pitch |
Major Diameter |
Minor Diameter |
Gage Length |
| Inch |
mm |
Inch |
mm |
Inch |
Mm |
Inch |
mm |
| 1/8 |
28 |
0.0357 |
0.907 |
0.383 |
9.728 |
0.3372 |
8.565 |
0.1563 |
3.97 |
| 1/4 |
19 |
0.0526 |
1.337 |
0.518 |
13.157 |
0.4506 |
11.445 |
0.2367 |
6.012 |
| 3/8 |
19 |
0.0526 |
1.337 |
0.656 |
16.662 |
0.5886 |
14.95 |
0.25 |
6.35 |
| 1/2 |
14 |
0.0714 |
1.814 |
0.825 |
20.955 |
0.7336 |
18.633 |
0.3214 |
8.164 |
| 3/4 |
14 |
0.0714 |
1.814 |
1.041 |
26.441 |
0.9496 |
24.12 |
0.375 |
9.525 |
| 1 |
11 |
0.0909 |
2.309 |
1.309 |
33.249 |
1.1926 |
30.292 |
0.4091 |
10.391 |
| 1 ¼ |
11 |
0.0909 |
2.309 |
1.65 |
41.91 |
1.5336 |
38.953 |
0.5 |
12.7 |
| 1 ½ |
11 |
0.0909 |
2.309 |
1.882 |
47.803 |
1.7656 |
44.846 |
0.5 |
12.7 |
| 2 |
11 |
0.0909 |
2.309 |
2.347 |
59.614 |
2.2306 |
56.657 |
0.625 |
15.875 |
| 2 ½ |
11 |
0.0909 |
2.309 |
2.96 |
75.184 |
2.8436 |
72.227 |
0.6875 |
17.463 |
| 3 |
11 |
0.0909 |
2.309 |
3.46 |
87.884 |
3.3436 |
84.927 |
0.8125 |
20.638 |
| 4 |
11 |
0.0909 |
2.309 |
4.45 |
113.03 |
4.3336 |
110.073 |
|
|
NPT
NPT stands for National Pipe Thread and is an American standard thread. It may also be reffered to as MPT , MNPT or NPT (M) for male external threads and FPT, FNPT or NPT(F) for female interal threads. A thread sealant must always be used to achieve a leak free seal (except for NPTF). It is also based on Trade Size rather than actual diameter (similar to BSP in this regard).
Both threads have the same pitch, angle (60 degrees) and shape (flat peaks and valleys).
The below table gives the Threads Per Inch, Pithc and Major Diameter for NPT Threads.
| Trade Size |
Threads per inch |
Pitch |
Major Diameter (O.D) |
| Inch |
mm |
Inch |
mm |
| 1/8 |
27 |
0.03704 |
0.94082 |
0.405 |
10.29 |
| 1/4 |
18 |
0.05556 |
1.41122 |
0.54 |
13.72 |
| 3/8 |
18 |
0.05556 |
1.41122 |
0.675 |
17.15 |
| 1/2 |
14 |
0.07143 |
1.81432 |
0.84 |
21.34 |
| 3/4 |
14 |
0.07143 |
1.81432 |
1.05 |
26.67 |
| 1 |
11 ½ |
0.08696 |
2.20878 |
1.315 |
33.4 |
| 1 ¼ |
11 ½ |
0.08696 |
2.20878 |
1.66 |
42.16 |
| 1 ½ |
11 ½ |
0.08696 |
2.20878 |
1.9 |
48.26 |
| 2 |
11 ½ |
0.08696 |
2.20878 |
2.375 |
60.33 |
| 2 ½ |
8 |
0.125 |
3.175 |
2.875 |
73.03 |
| 3 |
8 |
0.125 |
3.175 |
3.5 |
88.9 |
| 4 |
8 |
0.125 |
3.175 |
4.5 |
114.3 |
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