Square Head Bolts

It was the square head machine bolts that were the industry standard before Hex bolts became prominent. However, presently, square bolts are used largely for aesthetic purposes, offering a rustic finish to a new structure. Besides, they are also used to match existing fasteners of older structures. Square leg screws are also sometimes used to serve such purposes. Machine bolts or cross arm bolts are supplied primarily to the utility industry where they include an added cone point.

Manufacturing

BBI manufactures superior quality square bolts. With a diameter of 1/2″ – 2″, these bolts fulfill most specifications of the ASTM, SAE and AASHTO. In fact, we can even create special tooling to help produce nonstandard bolt heads / head dimensions with the preferred logo and/or name. We also stock square head blanks that can be used for small orders or expedited deliveries.

   


Stock

baseline Bolt does not stock any square head machine bolts, and in most cases, square head bolts are not readily available through fastener distributors. Typically, square head bolts will need to be custom manufactured.

Standard Thread Lengths

Bolt lengths < 6″: Thread length = (2 X diameter) + 1/4″
Bolt lengths > 6″: Thread length = (2 X diameter) + 1/2″

Square Head Dimensions

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

* 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.

Dimensions per ASME B18.2.1 1996