NPT tap drill chart
Drill sizes for tapping NPT pipe threads with no reamer step. If you ream first, use the smaller drill your tap or reamer maker lists.
| Pipe size | Threads per inch | Tap drill | Inches | mm |
|---|---|---|---|---|
| 1/16 NPT | 27 | Letter D | 0.2460 | 6.25 |
| 1/8 NPT | 27 | Letter Q | 0.3320 | 8.43 |
| 1/4 NPT | 18 | 7/16" | 0.4375 | 11.11 |
| 3/8 NPT | 18 | 37/64" | 0.5781 | 14.68 |
| 1/2 NPT | 14 | 23/32" | 0.7188 | 18.26 |
| 3/4 NPT | 14 | 59/64" | 0.9219 | 23.42 |
| 1 NPT | 11.5 | 1-5/32" | 1.1562 | 29.37 |
| 1-1/4 NPT | 11.5 | 1-1/2" | 1.5000 | 38.10 |
| 1-1/2 NPT | 11.5 | 1-47/64" | 1.7344 | 44.05 |
| 2 NPT | 11.5 | 2-7/32" | 2.2188 | 56.36 |
Tools for this job
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