Overview
NPT – National Pipe Taper – ANSI/ASME B1.20.1-1983
NPSM – National Pipe Straight Mechanical – ANSI/ASME B1.20.1-1983
Note: Thread size refers to the nominal bore of the pipe. Subtract approx. ¼″ (6mm) from thread diameter measurement for nominal pipe size.
Sealing Methods
NPT
NPT to NPT
NPT to fixed NPT female sealing is made through direct metal to metal contact. The use of Volz Thread Sealant is recommended.
NPSM
NPT to NPSM
NPT male with conical 30° seat (60° included angle) seal against matching conical 30° seat of NPSM female swivel.
Identification Table
| Nominal Pipe Size | Threads Per Inch | OD of Thread (mm) | OD of Thread (inch) |
|---|---|---|---|
| 1/16″ | 27 | 7.94 | 0.3125 |
| 1/8″ | 27 | 10.29 | 0.405 |
| 1/4″ | 18 | 13.72 | 0.540 |
| 3/8″ | 18 | 17.15 | 0.675 |
| 1/2″ | 14 | 21.34 | 0.840 |
| 3/4″ | 14 | 26.67 | 1.050 |
| 1″ | 11½ | 33.40 | 1.315 |
| 1¼″ | 11½ | 42.16 | 1.660 |
| 1½″ | 11½ | 48.26 | 1.900 |
| 2″ | 11½ | 60.33 | 2.375 |