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- ANSI B18.2.1/BS1083 Specifications
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Imperial Hex Head Bolt Specifications
- B Measurement varies according to the length of bolt
- All measurements are in millimeters (mm)
- For Hex Set Screws disregard B measurement as they are fully threaded
ANSI B18.2.1 Specifications
| D | B to 6" | B over 6" | K | S |
| 1/4 | 19.05 | 25.4 | 4.14 | 11.13 |
| 5/16 | 22.22 | 28.57 | 5.36 | 12.70 |
| 3/8 | 25.4 | 31.75 | 6.17 | 14.27 |
| 7/16 | 28.57 | 34.9 | 7.39 | 15.90 |
| 1/2 | 31.75 | 38.1 | 8.20 | 19.05 |
| 5/8 | 38.1 | 44.5 | 10.24 | 23.83 |
| 3/4 | 44.45 | 50.8 | 12.27 | 28.58 |
| 7/8 | 50.8 | 57.15 | 14.30 | 33.32 |
| 1" | 57.15 | 63.50 | 15.92 | 38.1 |
BS1083 Specifications
| D | B to 6" | B over 6" | K | S |
| 1/4 | 19.05 | 25.4 | 4 | 10 |
| 5/16 | 22.24 | 28.57 | 5 | 12 |
| 3/8 | 25.4 | 31.75 | 5.55 | 14 |
| 7/16 | 28.57 | 34.93 | 7 | 17 |
| 1/2 | 31.75 | 38.1 | 7.65 | 19 |
| 5/8 | 38.10 | 44.5 | 9.35 | 23 |
* Use this information as a guide only