Historical & Obsolete
Sellers Thread (US Standard)
The 19th-century US standard that preceded the Unified thread.
- Flank angle
- 60°
- Sizes listed
- 27
- Range
- 1/4" - 20 – 6" - 2 1/4
| Nominal Diameter | Major Diameter Inch | Major Diameter mm | Tapping Drill Size mm | TPI | Pitch mm |
|---|---|---|---|---|---|
| 1/4" - 20 | 0.250 | 6.350 | 4.72 | 20 | 1.270 |
| 5/16" - 18 | 0.313 | 7.938 | 6.13 | 18 | 1.411 |
| 3/8" - 16 | 0.375 | 9.525 | 7.49 | 16 | 1.587 |
| 7/16" - 14 | 0.438 | 11.113 | 8.79 | 14 | 1.814 |
| 1/2" - 13 | 0.500 | 12.700 | 9.99 | 13 | 1.954 |
| 5/8" - 11 | 0.625 | 15.875 | 12.92 | 11 | 2.309 |
| 3/4" - 10 | 0.750 | 19.050 | 15.80 | 10 | 2.540 |
| 7/8" - 9 | 0.875 | 22.225 | 18.61 | 9 | 2.822 |
| 1" - 8 | 1.000 | 25.400 | 21.33 | 8 | 3.175 |
| 1 1/8" - 7 | 1.125 | 28.575 | 23.93 | 7 | 3.628 |
| 1 1/4" - 7 | 1.250 | 31.750 | 27.10 | 7 | 3.628 |
| 1 3/8" - 6 | 1.375 | 34.925 | 29.50 | 6 | 4.233 |
| 1 1/2" - 6 | 1.500 | 38.100 | 32.68 | 6 | 4.233 |
| 1 5/8" - 5 1/2 | 1.625 | 41.275 | 34.77 | 5.5 | 4.618 |
| 1 3/4" - 5 | 1.750 | 44.450 | 37.94 | 5 | 5.080 |
| 1 7/8" - 5 | 1.875 | 47.625 | 40.40 | 5 | 5.080 |
| 2" - 4 1/2 | 2.000 | 50.800 | 43.57 | 4.5 | 5.644 |
| 2 1/4" - 4 1/2 | 2.250 | 57.150 | 49.02 | 4.5 | 5.644 |
| 2 1/2" - 4 | 2.500 | 63.500 | 55.37 | 4 | 6.350 |
| 2 3/4" - 4 | 2.750 | 69.850 | 60.55 | 4 | 6.350 |
| 3" - 3 1/2 | 3.000 | 76.200 | 66.90 | 3.5 | 7.257 |
| 3 1/4" - 3 1/2 | 3.250 | 82.550 | 72.57 | 3.5 | 7.257 |
| 3 1/2" - 3 1/4 | 3.500 | 88.900 | 78.92 | 3.25 | 7.815 |
| 3 3/4" - 3 | 3.750 | 95.250 | 84.40 | 3 | 8.467 |
| 4" - 3 | 4.000 | 101.600 | 90.75 | 3 | 8.467 |
| 5" - 2 1/2 | 5.500 | 127.000 | 115.20 | 2.5 | 10.160 |
| 6" - 2 1/4 | 6.000 | 152.400 | 139.40 | 2.25 | 11.289 |
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.