- This page provided the thread dimensions of 3/8 - 18 NPTF
- NPTF stands for National Pipe Thread Fuel, based on ASTM B1.20.3.
- It is also called Dryseal Pipe Thread.
- It is a variation of the more popular NPT thread standard based on ASTM B1.20.1.
- Learn more about NPTF and the difference between NPTF and NPT
3/8 - 18 NPTF - External Basic Thread Dimensions
For interpertations of the terms scroll down to the drawings below the table
| Property | Inch | mm |
|---|---|---|
| Nominal Pipe Size(∅) | 3/8 | |
| Pipe Outside Diameter (D) | 0.675 | 17.15 |
| Fitting Outside Diameter (D2) | 0.681 | 17.3 |
| Pitch - TPI (P) | 18 | ... |
| Pitch - Distance (P) | 0.055556 | 1.4111 |
| Thread Tapper Angle (β) | 1.7893 ° | |
| Thread V half Angle (α) | 30 ° | |
| Height of sharp V (H) | 0.048110 | 1.222 |
| Thread Height (h) | 0.03946 | 1.002 |
| Root Truncation (fr) | 0.0052 | 0.132 |
| Crest Truncation (fc) | 0.00345 | 0.088 |
| End of Thread Pitch Diameter (E0) | 0.61201 | 15.545 |
| Hand-Tight Engagement Length (L1) | 0.24000 | 6.096 |
| Pitch Diameter at L1 plane (E1) | 0.62701 | 15.926 |
| Length of Last usefull Thread (L2) | 0.40780 | 10.358 |
| Pitch Diameter at L2 plane (E2) | 0.63750 | 16.193 |
| Overall Thread Length (L2 + 3P) | 0.56250 | 14.288 |
| Length of Vanish threads (V) | 0.15470 | 3.929 |
3/8 - 18 NPTF - External Thread Drawing
Overview Drawing
Profile Drawing
3/8 - 18 NPTF - Internal Basic Thread Dimensions
For interpertations of the terms scroll down to the drawings below the table
| Property | Inch | mm |
|---|---|---|
| Nominal Pipe Size(∅) | 3/8 | |
| Pitch - TPI (P) | 18 | ... |
| Pitch - Distance (P) | 0.055556 | 1.4111 |
| Thread Tapper Angle (β) | 1.7893 ° | |
| Thread V half Angle (α) | 30 ° | |
| Height of sharp V (H) | 0.6810 | 1.411 |
| Thread Height (h) | 0.03946 | 1.002 |
| Root Truncation (fr) | 0.0052 | 0.132 |
| Crest Truncation (fc) | 0.00345 | 0.088 |
| Pitch Diameter at the end of the thread (E1) | 0.62701 | 15.926 |
| Hand-Tight Engagement Length (L1) | 0.24000 | 6.096 |
| Length of Wrenching Allowance (L3) | 0.16670 | 4.234 |
| Pitch Diameter at L3 plane (E3) | 0.60160 | 15.281 |
| Ideal Tap Drill Size | 0.56590 | 14.374 |
| Nearest standard Inch drill | 9 /1 6 (0.562 |
3/8 - 18 NPTF - Internal Thread Drawing
Overview Drawing
Profile Drawing
3/8 - 18 NPTF - Tolerances
| Property | Minimum | Maximum |
|---|---|---|
| Thread Height (h) | 0.037710" (0.958 mm) | 0.041210" (1.047 mm) |
| Root Truncation (fr) | 0.00430" (0.109 mm) | 0.00610" (0.155 mm) |
| Crest Truncation (fc) | 0.00260" (0.066 mm) | 0.00430" (0.109 mm) |
| Tapper Angle (β) | 1.643° | 1.934° |
| Thread Head half Angle (α) | 28° | 32° |
* All other dimensions can be controlled only with gauges.
