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