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Square Head Bolt

Bolts with a square shaped head rather than the standard hexagonal shape. This creates a larger bearing surface for wrenching.

square bolt

Dimensions

ASME B18.2.1

Thread Dia. Across Flats Thread Length Thread Length > 6"
1/4 0.362 - 0.375 3/4 1
5/16 0.484 - 0.500 7/8 1 1/8
3/8 0.544 - 0.562 1 1 1/4
7/16 0.603 - 0.625 1 1/8 1 3/8
1/2 0.725 - 0.750 1 1/4 1 1/2
5/8 0.906 - 0.938 1 1/2 1 3/4
3/4 1.088 - 1.125 1 3/4 2
7/8 1.269 - 1.312 2 2 1/4
1 1.450 - 1.500 2 1/4 2 1/2
1 1/8 1.631 - 1.688 2 1/2 2 3/4
1 1/4 1.812 - 1.875 2 3/4 3
1 3/8 1.994 - 2.062 3 3 1/4
1 1/2 2.175 - 2.250 3 1/4 3 1/2