Round head bolts (button head) are commonly used in wood connections. Round head bolts are similar to carriage bolts, but without the square neck under the head. Because they are used with wood, round head bolts are rarely high strength and virtually always supplied in a standard ASTM A307 specification.

Manufacturing

Portland Bolt manufactures button head bolts from 12” through 114 ” diameter in most ASTM, AASHTO, and SAE specifications. Special tooling can be created to produce nonstandard head dimensions, button head bolts larger than 114” in diameter, or bolt heads with your company’s name and/or logo.

Standard Thread Length

Bolt lengths ≤ 6″: Thread length = (2 X diameter) + 14
Bolt lengths > 6″: Thread length = (2 X diameter) + 12

Round Head Bolt Dimensions

Click table to show drawinground-head
Bolt Diameter C H
Head Diameter Head Height
Max Min Max Min
12 1.094 1.032 0.270 0.250
58 1.344 1.219 0.344 0.313
34 1.594 1.469 0.406 0.375
78 1.844 1.719 0.469 0.438
1 2.094 1.969 0.531 0.500
114 2.850 0.531 0.500

*Dimensions per ASME B18.5 1990 (R 1998) cover diameters up to 1". Bolts over 1" use custom head dimensions.