BSP
| Size (inch) | D1 mm (") | D2 mm (") | P mm (") |
| 1/2" | 20.96 (0.83) | 18.63 (0.73) | 1.81 (0.07) |
| 3/4" | 26.41 (1.04) | 24.12 (0.95) | 1.81 (0.07) |
| 1" | 33.25 (1.31) | 30.29 (1.19) | 2.31 (0.09) |
| 1"1/4 | 41.6 (1.64) | 39.3 (1.55) | 2.31 (0.09) |
| 1"1/2 | 47.80 (1.88) | 44.85 (1.77) | 2.31 (0.09) |
| 2" | 59.61 (2.35) | 56.66 (2.23) | 2.31 (0.09) |
| 3" | 87.88 (3.46) | 84.93 (3.34) | 2.31 (0.09) |
| 4" | 113.03 (4.45) | 110.07 (4.33) | 2.31 (0.09) |
NPT
| Size (inch) | D1 mm (") | D2 mm (") | P mm (") |
| 1/2" | 21.22 (0.84) | 18.32 (0.72) | 1.81 (0.07) |
| 3/4" | 26.57 (1.05) | 23.77 (0.93) | 1.81 (0.07) |
| 1" | 33.23 (1.31) | 29.69 (1.17) | 2.21 (0.09) |
| 1"1/2 | 48.05 (1.89) | 44.52 (1.75) | 2.21 (0.09) |
| 2" | 60.09 (2.37) | 56.56 (2.23) | 2.21 (0.09) |
| 3" | 88.61 (3.49) | 83.53 (3.29) | 3.18 (0.13) |
| 4" | 113.97 (4.49) | 108.89 (4.29) | 3.18 (0.13) |
Known as Gas Thread or BSP, this thread is distinguished by its fine thread. The name BSP comes from British Standard Pipe (or British Standard Pipe Thread).
These gas threads are of two types:
- cylindrical: they are mounted in the same cylindrical thread. Sealing is provided by a built-in ring seal (or washer seal).
- conical: they are mounted in the same cylindrical or conical thread. Sealing is ensured by a pre-coating in the thread.
Designation of threads
- BSP cylindrical: G followed by the name, according to ISO 228-1 - example: 1/8" BSP cylindrical thread > G 1 / 8
- BSP tapered: R followed by the designation, according to ISO 7-1 - example: 1/8" BSP tapered thread > R 1 / 8
- internal threads:
BSP cylindrical: G followed by the designation
BSP tapered: Rc followed by the designation
Cylindrical BSP connection (thread angle 55°):
The sealing is made by the cone in cone connection (60°),
Cylindrical BSP (or GAZ) thread,
dimensions in BSP inches and fractions of BSP inches,
pitch in number of threads per inch.