Compressed air.
Thread size conversion table
| Thread size in inch | Outer Ø (mm) | Core Ø (mm) |
| 1/16 | 7.723 | 6.561 |
| 1/8 | 9.728 | 8.566 |
| 1/4 | 13.157 | 11.445 |
| 3/8 | 16.662 | 14.950 |
| 1/2 | 20.955 | 18.631 |
| 5/8 | 22.911 | 20.587 |
| 3/4 | 26.441 | 24.117 |
| 7/8 | 30.201 | 27.877 |
| 1 | 33.249 | 30.291 |
| 1 1/8 | 37.897 |
34.939 |
| 1 1/4 | 41.910 | 38.952 |
| 1 1/2 | 47.803 | 44.845 |
| 1 3/4 | 53.746 | 50.788 |
| 2 | 59.614 | 56.656 |
| 2 1/4 | 65.710 | 62.752 |
| 2 1/2 | 75.184 | 72.226 |
| 2 3/4 | 81.534 | 78.576 |