The carriage bolt is a round head bolt with a square shoulder under the head and a unified thread pitch, made from low or medium carbon steel
It is designed to keep the bolt from turning when a nut is being tightened, and the short neck is used with sheet metal where a standard size neck would create an obstruction
The material is AISI 1006-1050 or equivalent steel, with a hardness of Rockwell B70-B100, a proof load of 33,000 psi, a tensile strength of 60,000 psi min, a yield strength of 36,000 psi min, an elongation of 18% min, and a reduction of area of 35% min
The minimum length of thread shall be equal to twice the basic bolt diameter plus .025" for bolts < 6"
The top of the carriage bolt has a square neck that resists turning once the bolt is fastened, and the flat end means that a washer and nut are used
It is important to use washers with carriage bolts to prevent damage when using the nut to pull the bolt through the material
