| NPT ‐ National Pipe Thread Taper ‐ ANSI B1.20.1 | |||||
| Pipe Size (inches) | Threads/Inch | Approx. Length of Thread (inches) | Approx Number of Threads to be cut | Nominal Outside Pipe Diameter (inches) | Tap Drill |
| 1/8" | 27 | 3/8" | 10 | 0.405" | |
| 1/4" | 18 | 5/8" | 11 | 0.540" | 7/16" |
| 3/8" | 18 | 5/8" | 11 | 0.675" | 37/64" |
| 1/2" | 14 | 3/4" | 10 | 0.840" | 23/32" |
| 3/4" | 14 | 3/4" | 10 | 1.050" | 59/64" |
| 1" | 11‐1/2 | 7/8" | 10 | 1.315" | 1‐5/32" |
| 1‐1/4" | 11‐1/2 | 1" | 11 | 1.660" | 1‐1/2" |
| 1‐1/2" | 11‐1/2 | 1" | 11 | 1.900" | 1‐47/64" |
| 2" | 11‐1/2 | 1" | 11 | 2.375" | 2‐7/32" |
| 2‐1/2" | 8 | 1‐1/2" | 12 | 2.875" | 2‐5/8" |
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