Carriage bolts (round head with a 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 imported stock carriage bolts have a thread length of 6″ and are fully threaded when the bolt length is 6″ or shorter.

Stock

Diameters: 1/2″ – 3/4″
Lengths: 18″ maximum
Origin: Import
Finish: Plain and hot-dip galvanized

Carriage Dimensions

Click table to show drawing
Bolt DiameterDCHPF
Body DiameterHead DiameterHead HeightSquare WidthSquare Depth
MaxMinMaxMinMaxMinMaxMinMaxMin
1⁄20.5150.4831.0941.0320.2700.2500.5150.4920.2810.250
5⁄80.6420.6051.3441.2190.3440.3130.6420.6160.3440.313
3⁄40.7680.7291.5941.4690.4060.3750.7680.7410.4060.375
7⁄80.8950.8521.8441.7190.4690.4380.8950.8650.4690.438
11.0220.9762.0941.9690.5310.5001.0220.9900.5310.500
11⁄4*1.2772.8500.5310.5001.2500.625
*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
61902619074
81903319082
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.