Pipe Threads
American Standard Taper Pipe Threads (NPT)
| Nominal Size (ID) |
Actual OD |
Close Fraction |
Threads per inch |
Length of engagement (hand tight) |
Hand tight turns |
Wrench make up turns |
Length of effective thread |
| 1/16 | 0.3125 | 5/16 | 27 | 0.16 | 0.2611 | ||
| 1/8 | 0.405 | 13/32 | 27 | 0.18 | 4 1/2 | 2 1/2 | 0.26 |
| 1/4 | 0.54 | 17/32 | 18 | 0.2 | 4 | 3 | 0.401 |
| 3/8 | 0.675 | 11/16 | 18 | 0.24 | 4 1/2 | 3 | 0.408 |
| 1/2 | 0.84 | 13/16 | 14 | 0.32 | 4 1/2 | 3 | 0.534 |
| 3/4 | 1.05 | 1 1/16 | 14 | 0.34 | 4 1/2 | 3 | 0.546 |
| 1 | 1.315 | 1 3/16 | 1 1.5 | 0.4 | 4 1/2 | 3 1/4 | 0.682 |
| 1 1/4 | 1.66 | 1 5/8 | 11.5 | 0.42 | 4 1/2 | 3 1/4 | 0.707 |
| 11/2 | 1.9 | 1 7/8 | 11.5 | 0.42 | 4 1/2 | 3 1/4 | 0.724 |
| 2 | 2.375 | 2 3/8 | 11.5 | 0.436 | 5 | 3 | 0.756 |
| 2 1/2 | 2.875 | 2 7/8 | 8 | 0.682 | 5 1/2 | 3 | 1.136 |
| 3 | 3.5 | 3 1/2 | 8 | 0.766 | 6 | 3 | 1.2 |
| 3 1/2 | 4 | 4 | 8 | 0.821 | 6 1/2 | 3 1/2 | 1.25 |
| 4 | 4.5 | 4 1/2 | 8 | 0.844 | 6 3/4 | 3 1/2 | 1.3 |
| 5 | 5.563 | 5 1/2 | 8 | 0.937 | 7 1/2 | 3 3/4 | 1.4063 |
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