US Standard Thread Pitch
US Standard Threads are measured in TPI (Threads per Inch). They are measured by finding the number of thread crests in 1" of threads. They are separated into Coarse (NC, National Coarse) and Fine (NF, National Fine) threads.
Other Names: Imperial, Inch, Fractional, Unified
| Coarse Thread - NC | ||
|---|---|---|
| Thread | Decimal | Tap Drill |
| 4-40 | 0.1120 | 43, 3/32 |
| 6-32 | 0.1380 | 36, 7/64 |
| 8-32 | 0.1640 | 29 |
| 10-24 | 0.1900 | 25 |
| 12-24 | 0.2160 | 17, 11/64 |
| 1/4-20 | 0.2500 | 7, 13/64 |
| 5/16-18 | 0.3125 | F |
| 3/8-16 | 0.3750 | 5/16 |
| 7/16-14 | 0.4375 | U, 23/64 |
| 1/2-13 | 0.5000 | 27/64 |
| 9/16-12 | 0.5625 | 31/64 |
| 5/8-11 | 0.6250 | 17/32 |
| 3/4-10 | 0.7500 | 21/32 |
| 7/8-9 | 0.8750 | 49/64 |
| 1-8 | 1.0000 | 7/8 |
| Thread | Decimal | Tap Drill |
| 1 1/8-7 | 1.1250 | 63/64 |
| 1 1/4-7 | 1.2500 | 1 7/64 |
| 1 3/8-6 | 1.3750 | 1 7/32 |
| 1 1/2-6 | 1.5000 | 1 11/32 |
| 1 3/4-5 | 1.7500 | 1 9/16 |
| 2-4.5 | 2.000 | 1 25/32 |
| 2 1/4-4.5 | 2.2500 | |
| 2 1/2-4 | 2.5000 | |
| 2 3/4-4 | 2.7500 | |
| 3-4 | 3.0000 | |
| 3 1/4-4 | 3.2500 | |
| 3 1/2-4 | 3.5000 | |
| 3 3/4-4 | 3.7500 | |
| 4-4 | 4.0000 | |
| Fine Thread - NF | ||
|---|---|---|
| Thread | Decimal | Tap Drill |
| 4-48 | 0.1120 | 42, 3/32 |
| 6-40 | 0.1380 | 33 |
| 8-36 | 0.1640 | 29, 9/64 |
| 10-32 | 0.1900 | 21, 5/32 |
| 12-28 | 0.2160 | 15, 16 |
| 1/4-28 | 0.2500 | 3, 7/32 |
| 5/16-24 | 0.3125 | I |
| 3/8-24 | 0.3750 | Q |
| 7/16-20 | 0.4375 | 25/64 |
| 1/2-20 | 0.5000 | 29/64 |
| 9/16-18 | 0.5625 | 33/64 |
| 5/8-18 | 0.6250 | 37/64 |
| 3/4-16 | 0.7500 | 11/16 |
| 7/8-14 | 0.8750 | 13/16 |
| 1-12 | 1.0000 | 59/64 |
| Thread | Decimal | Tap Drill |
| 1 1/8-12 | 1.1250 | 1 3/16 |
| 1 1/4-12 | 1.2500 | 1 11/64 |
| 1 3/8-12 | 1.3750 | 1 19/64 |
| 1 1/2-12 | 1.5000 | 1 27/64 |