Carriage bolts (round head with square neck) are commonly used in wood connections. The square neck under the round head will seat into the hole in the wood to prevent the head from turning. Because they are used with wood, carriage bolts are rarely high strength and virtually always supplied in a standard ASTM A307 specification.

Manufacturing

Portland Bolt manufactures carriage bolts from 1/2″ diameter through 1-1/4″ diameter in most ASTM, AASHTO, and SAE specifications. Special tooling can be created to produce nonstandard head dimensions, carriage bolts larger than 1″ in diameter, 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 carriage bolts have extended thread length.

Stock

Diameters: 3/8″ – 3/4″
Lengths: 18″ maximum
Origin: Import
Finish: Plain and hot-dip galvanized

Carriage Dimensions

Click table to show drawing
Bolt Diameter D C H P F
Body Diameter Head Diameter Head Height Square Width Square Depth
Max Min Max Min Max Min Max Min Max Min
12 0.515 0.483 1.094 1.032 0.270 0.250 0.515 0.492 0.281 0.250
58 0.642 0.605 1.344 1.219 0.344 0.313 0.642 0.616 0.344 0.313
34 0.768 0.729 1.594 1.469 0.406 0.375 0.768 0.741 0.406 0.375
78 0.895 0.852 1.844 1.719 0.469 0.438 0.895 0.865 0.469 0.438
1 1.022 0.976 2.094 1.969 0.531 0.500 1.022 0.990 0.531 0.500
114* 1.277 2.850 0.531 0.500 1.250 0.625
*Dimensions per ASME B18.5 1990 (R 1998) cover diameters up to 1". Bolts over 1" use custom head dimensions.

Stock Carriage Bolts

Length (in.) Diameter
3/8" 1/2"
Galvanized
3 - 19060
4 - 19065
6 19026 19074
8 19033 19082
These sizes are readily available in the marketplace and Portland Bolt stocks many of them in varying quantities. If you require a size that is not listed, Portland Bolt will manufacture them.