Whitworth's Standard Screw Threads for Bolts (in)
| Diameter
of Fractional Sizes | Bolt
Decimal Sizes | Number
of Threads per Inch | Diameter
at Bottom of Thread | Distance
Across Flat | Distance
Across Corners | Thickness
of Bolt Head | Thickness
of Nut |
|---|---|---|---|---|---|---|---|
| 1/4 | 0.25 | 20 | 0.1860 | 0.525 | 0.6062 | 0.2187 | 1/4 |
| 5/16 | 0.3125 | 18 | 0.2414 | 0.6014 | 0.6944 | 0.2734 | 5/16 |
| 3/8 | 0.375 | 16 | 0.2950 | 0.7094 | 0.8191 | 0.3281 | 3/8 |
| 7/16 | 0.4375 | 14 | 0.3460 | 0.8204 | 0.9473 | 0.3828 | 7/16 |
| 1/2 | 0.5 | 12 | 0.3933 | 0.9191 | 1.0612 | 0.4375 | 1/2 |
| 9/16 | 0.5625 | 12 | 0.4558 | 1.011 | 1.1674 | 0.4921 | 9/16 |
| 5/8 | 0.625 | 11 | 0.5086 | 1.101 | 1.2713 | 0.5468 | 5/8 |
| 11/16 | 0.6875 | 11 | 0.5711 | 1.2011 | 1.3869 | 0.6015 | 11/16 |
| 3/4 | 0.75 | 10 | 0.6219 | 1.3012 | 1.5024 | 0.6562 | 3/4 |
| 13/16 | 0.8125 | 10 | 0.6844 | 1.39 | 1.6050 | 0.7109 | 13/16 |
| 7/8 | 0.875 | 9 | 0.7327 | 1.4788 | 1.7075 | 0.7656 | 7/8 |
| 1 | 1.1 | 8 | 0.8399 | 1.6701 | 1.9284 | 0.875 | 1 |
| 1 1/8 | 1.125 | 7 | 0.9420 | 1.8605 | 2.1483 | 0.9843 | 1 1/8 |
| 1 1/4 | 1.25 | 7 | 1.0670 | 2.0483 | 2.3651 | 1.0937 | 1 1/4 |
| 1 3/8 | 1.375 | 6 | 1.1616 | 2.2146 | 2.5571 | 1.2031 | 1 3/8 |
| 1 1/2 | 1.5 | 6 | 1.2866 | 2.4134 | 2.7867 | 1.3125 | 1 1/2 |
| 1 5/8 | 1.625 | 5 | 1.3689 | 2.5763 | 2.9748 | 1.4218 | 1 5/8 |
| 1 3/4 | 1.75 | 5 | 1.4939 | 2.7578 | 3.1844 | 1.5312 | 1 3/4 |
| 2 | 2.0 | 4.5 | 1.7154 | 3.1491 | 3.6362 | 1.75 | 2 |
| 2 1/4 | 2.25 | 4 | 1.9298 | 3.546 | 4.0945 | 1.9687 | 2 1/4 |
| 2 1/2 | 2.5 | 4 | 2.1798 | 3.984 | 4.4964 | 2.1875 | 2 1/2 |
| 2 3/4 | 2.75 | 3.5 | 2.3841 | 4.101 | 4.8278 | 2.4062 | 2 3/4 |
| 3 | 3.0 | 3.5 | 2.6341 | 4.531 | 5.2319 | 2.625 | 3 |
| 3 1/4 | 3.25 | 3.25 | 2.8560 | 4.85 | 5.6002 | 2.843 | 3 1/4 |
| 3 1/2 | 3.5 | 3.25 | 3.1060 | 5.175 | 5.9755 | 3.062 | 3 1/2 |
| 3 3/4 | 3.75 | 3 | 3.3231 | 5.55 | 6.4085 | 3.281 | 3 3/4 |
| 4 | 4.0 | 3 | 3.5731 | 5.95 | 6.8704 | 3.5 | 4 |
| 4 1/2 | 4.5 | 2.875 | 4.0546 | 6.825 | 7.8819 | 3.937 | 4 1/2 |
| 5 | 5.0 | 2.75 | 4.5343 | 7.8 | 9.0066 | 4.375 | 5 |
| 5 1/2 | 5.5 | 2.625 | 5.0121 | 8.85 | 10.2190 | 4.812 | 5 1/2 |
| 6 | 6.0 | 2.5 | 5.4877 | 10 | 11.5470 | 5.25 | 6 |