Carriage Bolts

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.

Basic Bolt Diameter E A H O P
Body Diameter Head Diameter Head Height Square Width Square Depth
Max Min Max Min Max Min Max Min Max Min
•8 0.1640 0.173 0.157 0.328 0.298 0.102 0.083 0.169 0.155 0.108 0.078
10 0.1900 0.199 0.182 0.469 0.436 0.114 0.094 0.199 0.185 0.125 0.094
•12 0.2160 0.225 0.206 0.500 0.468 0.149 0.125 0.215 0.197 0.135 0.105
1/4 0.2500 0.260 0.237 0.594 0.563 0.145 0.125 0.260 0.245 0.156 0.125
5/16 0.3125 0.324 0.298 0.719 0.688 0.176 0.156 0.324 0.307 0.187 0.156
3/8 0.3750 0.388 0.360 0.844 0.782 0.208 0.188 0.388 0.368 0.219 0.188
7/16 0.4375 0.452 0.421 0.969 0.907 0.239 0.219 0.452 0.431 0.250 0.219
1/2 0.5000 0.515 0.483 1.094 1.032 0.270 0.250 0.515 0.492 0.281 0.250
5/8 0.6250 0.642 0.605 1.344 1.219 0.344 0.313 0.642 0.616 0.344 0.313
3/4 0.7500 0.768 0.729 1.594 1.469 0.406 0.375 0.768 0.741 0.406 0.375
 
Tolerance on Length Nominal Bolt Size Nominal Bolt Length
Up to 1 in., incl. Over 1 in. to 2-1/2 in., incl. Over 2-1/2 in. to 4 in., incl. Over 4 in. to 6 in., incl. Over 6 in.
No. 8 thru 3/8 +0.02 +0.02 +0.04 +0.06 +0.10
-0.03 -0.04 -0.06 -0.10 -0.18
7/16 and 1/2 +0.02 +0.04 +0.06 +0.08 +0.12
-0.03 -0.05 -0.08 -0.10 -0.18
9/16 thru 3/4 +0.02 +0.06 +0.08 +0.10 +0.14
-0.03 -0.08 -0.10 -0.10 -0.18