Square Head Machine Bolts

Square Head Machine bolts are used for fastening pole line hardware and line construction specialty products to crossarm poles and other structures as well as attaching the wooden crossarms to the pole. Square head machine bolts have an added semi-cone point and a thread length unique to pole line fasteners depending on the length of the bolts. Square head machine bolts have a square nut assembled.

square-machine-bolt-nut-dim-525

Click table to show drawing
Bolt Diameter D F C H
Body Diameter Width Across Flats Width Across Corners Height
Max Basic Max Min Max Min Basic Max Min
1⁄2 0.515 3⁄4 0.750 0.725 1.061 0.995 21⁄64 0.348 0.308
5⁄8 0.642 15⁄16 0.938 0.906 1.326 1.244 27⁄64 0.444 0.400
3⁄4 0.768 11⁄8 1.125 1.088 1.591 1.494 1⁄2 0.524 0.476
7⁄8 0.895 15⁄16 1.312 1.269 1.856 1.742 19⁄32 0.620 0.568
1 1.022 11⁄2 1.500 1.450 2.121 1.991 21⁄32 0.684 0.628
11⁄8 1.149 111⁄16 1.688 1.631 2.386 2.239 3⁄4 0.780 0.720
11⁄4 1.277 17⁄8 1.875 1.812 2.652 2.489 27⁄32 0.876 0.812
13⁄8 1.404 21⁄16 2.062 1.994 2.917 2.738 29⁄32 0.940 0.872
11⁄2 1.531 21⁄4 2.250 2.175 3.182 2.986 1 1.036 0.964
13⁄4* 29⁄16 13⁄16
2* 215⁄16 15⁄16

Dimensions per ASME B18.2.1 1996

* ASME only defines head dimensions up to 1-1/2". Dimensions for 1-3/4 and 2" are approximate and not covered under the ASME dimensional specifications.

Standard Thread Lengths

*Bolts shorter and/or smaller than those listed in the table shall have minimum thread lengths in accordance with American National Standard for Square and  Hex Bolts and Screws, B18.2.1*
Diameters Bolt length Thread length
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
 4" up to less than 8" 3"
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
  • 1-1/4"
 8" up to less than 12" 4"
  • 3/8"
  • 1/2"
  • 5/8"
  • 3/4"
  • 7/8"
  • 1"
  • 1-1/4"
 12" and over 6"