3-1/2-6NH vs 3-1/2-8 NPT: specs compared
Updated 05 September 2026.
107.77 mm
3-1/2-6NH wins on major diameter
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 101.6 mm.
| Spec | 3-1/2-6NH | 3-1/2-8 NPT |
|---|---|---|
| Designation | 3-1/2-6NH | 3-1/2-8 NPT |
| Major diameter | 107.77 mm | 101.6 mm |
| Threads per inch / pitch | 6 | 8 |
| Thread form | straight (parallel), 60 degree | tapered, 60 degree |
| Seals on | rubber gasket in the female swivel | on the thread flanks with PTFE tape |
Questions and answers
Which has the higher major diameter, 3-1/2-6NH or 3-1/2-8 NPT?
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 101.6 mm.
How do 3-1/2-6NH and 3-1/2-8 NPT compare?
On major diameter, 3-1/2-6NH leads: 107.77 mm versus 101.6 mm.