Countersunk bolts are used when a smooth surface is required. Common applications include: bridge decking, walkways, and railing.

Manufacturing

Portland Bolt manufactures countersunk bolts from 1/2″ diameter through 1-1/2″ diameter in most ASTM, AASHTO, and SAE specifications including, A307 Grade A, A449, and Grade 8. Countersunk bolts have a head angle of approximately 80 degrees. Bolts are available with and without a slot in the head. Special tooling can be created to produce nonstandard head dimensions or bolt heads with your company’s name and/or logo.

Standard Thread Length

Bolt lengths ≤ 6″: Thread length = (2 X diameter) + 1/4″
Bolt lengths > 6″: Thread length = (2 X diameter) + 1/2″
Note: Most stock hex bolts longer than 12″ in length will have 6″ of thread.

Countersunk Dimensions

Click table to show drawing
Bolt Diameter D F H
Body Diameter Head Diameter Head Height
Max Max Edge Sharp Min Edge Sharp Absolute Min Rounded Max Min
12 0.515 0.935 0.905 0.845 0.269 0.233
58 0.642 1.169 1.132 1.066 0.336 0.292
34 0.768 1.402 1.357 1.285 0.403 0.349
78 0.895 1.637 1.584 1.511 0.470 0.408
1 1.022 1.869 1.810 1.735 0.537 0.466
118 1.149 2.104 2.037 1.962 0.604 0.525
114 1.277 2.337 2.262 2.187 0.671 0.582
138 1.404 2.571 2.489 2.414 0.738 0.641
112 1.531 2.804 2.715 2.640 0.805 0.698

Dimensions per ASME B18.5 1990 (R 1998)