NPT American Taper Pipe Thread · ANSI/ASME B1.20.1
3" - 8 NPT Thread: Pitch, Tap Drill & Dimensions
3" - 8 NPT is a NPT American Taper Pipe Thread (ANSI/ASME B1.20.1) size, with a major diameter of 88.608 mm, 8 threads per inch (3.175 mm pitch). The tap drill is 81.50 mm.
| Major Diameter (mm) | 88.608 |
|---|---|
| Tapping Drill Size (mm) | 81.50 |
| TPI | 8 |
| Pitch (mm) | 3.175 |
| Flank angle | 60° |
| Taper | 1:16 |
Common questions
What size drill do I use to tap 3" - 8 NPT?
Use a 81.50 drill. This is the standard tap drill for 3" - 8 NPT; for hard materials or deep threads a slightly larger drill reduces tapping torque.
What is the pitch of 3" - 8 NPT?
The pitch of 3" - 8 NPT is 3.175, meaning the thread advances that distance in one full turn.
Where can I find other NPT American Taper Pipe Thread sizes?
The full NPT American Taper Pipe Thread table, with every size and a live filter, is on its standard page, and the Thread Finder searches all 73 standards at once.
Reference values; computed values use the ISO basic profile. Verify against the current standard before production use.