Unified Inch (UNC / UNF / UN)
20-UN Constant Pitch Series
Unified inch threads share the 60° profile with ISO metric but are sized in inches and specified by threads per inch (TPI), e.g. 1/4"-20 UNC.
- Standard
- ANSI/ASME B1.1
- Flank angle
- 60°
- Sizes listed
- 29
- Range
- 5/16" - 20-UN – 3" - 20-UN
| Nominal Diameter | Major Diameter Inch | Major Diameter mm | Tapping Drill Size mm | TPI | Pitch mm |
|---|---|---|---|---|---|
| 5/16" - 20-UN | 0.3125 | 7.9380 | 6.700 | 20 | 1.270 |
| 3/8" - 20-UN | 0.3750 | 9.5250 | 8.300 | 20 | 1.270 |
| 9/16" - 20-UN | 0.5625 | 14.288 | 13.100 | 20 | 1.270 |
| 5/8" - 20-UN | 0.6250 | 15.875 | 14.670 | 20 | 1.270 |
| 11/16" - 20-UN | 0.6875 | 17.462 | 16.250 | 20 | 1.270 |
| 1 1/16" - 20-UN | 1.0625 | 26.987 | 25.800 | 20 | 1.270 |
| 1 1/8" - 20-UN | 1.1250 | 28.575 | 27.370 | 20 | 1.270 |
| 1 3/16" - 20-UN | 1.1875 | 30.162 | 28.970 | 20 | 1.270 |
| 1 1/4" - 20-UN | 1.2500 | 31.750 | 30.550 | 20 | 1.270 |
| 1 5/16" - 20-UN | 1.3125 | 33.337 | 32.150 | 20 | 1.270 |
| 1 3/8" - 20-UN | 1.3750 | 34.925 | 33.700 | 20 | 1.270 |
| 1 7/16" - 20-UN | 1.4375 | 36.512 | 35.320 | 20 | 1.270 |
| 1 1/2" - 20-UN | 1.5000 | 38.100 | 36.890 | 20 | 1.270 |
| 1 9/16" - 20-UN | 1.5625 | 39.688 | 38.490 | 20 | 1.270 |
| 1 5/8" - 20-UN | 1.6250 | 41.275 | 40.080 | 20 | 1.270 |
| 1 11/16" - 20-UN | 1.6875 | 42.862 | 41.680 | 20 | 1.270 |
| 1 3/4" - 20-UN | 1.7500 | 44.450 | 43.250 | 20 | 1.270 |
| 1 13/16" - 20-UN | 1.8125 | 46.037 | 44.840 | 20 | 1.270 |
| 1 7/8" - 20-UN | 1.8750 | 47.625 | 46.420 | 20 | 1.270 |
| 1 15/16" - 20-UN | 1.9375 | 49.212 | 48.000 | 20 | 1.270 |
| 2" - 20-UN | 2.0000 | 50.800 | 49.580 | 20 | 1.270 |
| 2 1/8" - 20-UN | 2.1250 | 53.975 | 52.780 | 20 | 1.270 |
| 2 1/4" - 20-UN | 2.2500 | 57.150 | 56.030 | 20 | 1.270 |
| 2 3/8" - 20-UN | 2.3750 | 60.325 | 59.120 | 20 | 1.270 |
| 2 1/2" - 20-UN | 2.5000 | 63.500 | 62.300 | 20 | 1.270 |
| 2 5/8" - 20-UN | 2.6250 | 66.675 | 65.470 | 20 | 1.270 |
| 2 3/4" - 20-UN | 2.7500 | 69.850 | 68.670 | 20 | 1.270 |
| 2 7/8" - 20-UN | 2.8750 | 73.025 | 71.820 | 20 | 1.270 |
| 3" - 20-UN | 3.0000 | 76.200 | 75.000 | 20 | 1.270 |
Reference values only. Verify against the current edition of the governing standard before use in production drawings or manufacturing. Provided by Micro Components as a free engineering resource.