Square Head Machine Bolts

Square Head Machine bolts are used for fastening pole line hardware and line construction specialty products to cross arm poles and other structures as well as attaching the wooden cross arms 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 bolts length. 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
12 0.515 34 0.750 0.725 1.061 0.995 2164 0.348 0.308
58 0.642 1516 0.938 0.906 1.326 1.244 2764 0.444 0.400
34 0.768 118 1.125 1.088 1.591 1.494 12 0.524 0.476
78 0.895 1516 1.312 1.269 1.856 1.742 1932 0.620 0.568
1 1.022 112 1.500 1.450 2.121 1.991 2132 0.684 0.628
118 1.149 11116 1.688 1.631 2.386 2.239 34 0.780 0.720
114 1.277 178 1.875 1.812 2.652 2.489 2732 0.876 0.812
138 1.404 2116 2.062 1.994 2.917 2.738 2932 0.940 0.872
112 1.531 214 2.250 2.175 3.182 2.986 1 1.036 0.964
134* 2916 1316
2* 21516 1516

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"