External (pipe) Basic Thread Dimensions
For interpertations of the terms scroll down to the drawings below the table
| Property | Inch | mm |
|---|---|---|
| Nominal Pipe Size (Ø) | 3 1/2" | ... |
| Pipe Outside Diameter (D) | 4 | 101.6 |
| Pitch (TPI) (P) | 8.000 | 203.2 |
| Pitch (Distance) (P) | 0.125 | 3.175 |
| Thread Tapper Angle (ß) | 1.7893° | 1.7893° |
| Thread V half Angle (α) | 30° | 30° |
| Height of sharp V (H) | 0.108253 | 2.75 |
| Thread height (h) | 0.1 | 2.54 |
| Pitch Diameter at the Pipe's end (E0) | 3.8375 | 97.473 |
| Minor Diameter at the Pipe's end (K0) | 3.7375 | 94.933 |
| Hand-Tight Engagement Length (L1) | 0.821 | 20.853 |
| Pitch Diameter at L1 plane (E1) | 3.88881 | 98.776 |
| Length of Last Complete Thread (L5) | 1 | 25.4 |
| Pitch Diameter at L5 plane (E5) | 3.9 | 99.06 |
| Length of Last usefull Thread (L2) | 1.25 | 31.75 |
| Pitch Diameter at L2 plane (E2) | 3.91562 | 99.457 |
| Overall Thread Length (L4) | 1.6837 | 42.766 |
| Length of Vanish threads (V) | 0.4338 | 11.019 |
3 1/2-8 NPT - External (pipe) Drawing
Overview Drawing
Profile Drawing
3 1/2-8 NPT - Internal (Fitting) Basic Thread Dimensions
For interpertations of the terms scroll down to the drawings below the table
| Property | Inch | mm |
|---|---|---|
| Nominal Pipe Size (Ø) | 3 1/2" | ... |
| Pipe Outside Diameter (D) | 4 | 101.6 |
| Pitch (TPI) (P) | 8.000 | 203.2 |
| Pitch (Distance) (P) | 0.125 | 3.175 |
| Thread Tapper Angle (ß) | 1.7893° | 1.7893° |
| Thread V half Angle (α) | 30° | 30° |
| Height of sharp V (H) | 0.108253 | 2.75 |
| Thread height (h) | 0.1 | 2.54 |
| Pitch Diameter at the fitting's end (E1) | 3.88881 | 98.776 |
| Length of Hand-Tight Engagemen (L1) | 0.821 | 20.853 |
Length of Wrenching Allowance (L3) |
0.25 | 6.35 |
| Pitch Diameter at L3 plane (E3) | 3.82188 | 97.076 |
| Tap Drill Size (T) | N/A | N/A |
3 1/2-8 NPT - Internal (Fitting) Drawing
Overview Drawing
Profile Drawing
3 1/2-8 NPT - Tolerances
| Property | Minimum | Maximum |
|---|---|---|
| Thread Height (h) | 0.09275" (2.356 mm) | 0.1" (2.54 mm) |
| L1 gage Tolerance (+/- 1 Turn) (L1) | ... | 0.125" (3.175 mm) |
| Thread Truncation (f) | 0.0041" (0.104 mm) | 0.0078" (0.198 mm) |
| Tapper angle Variation (ß) | 1.641" ( ) | 2.089" ( ) |
| Thead V Half Angle (+/-) (α) | ... | 0.75" ( ) |
| Thread Height (h) | " (0 mm) | " (0 mm) |
| L1 gage Tolerance (+/- 1 Turn) (L1) | " ( ) | " ( ) |
| Thread Truncation (f) | " (0 mm) | " (0 mm) |
| Tapper angle Variation (ß) | " ( ) | " ( ) |
| Thead V Half Angle (+/-) (α) | " ( ) | " ( ) |
