Carriage bolts are extensively used for security fixings, such as locks and hinges, where the bolt must only be removable from one side. The smooth domed head and square nut below prevent the carriage bolt from being unlocked from the insecure side.
Carriage bolts were used in a carriage which was the basic transportation during inactive times. The wheels of the carriage are made of wood. It was in 1818 at Connecticut when a blacksmith named Mr. Micah Rugg invented a tool that will produce these specific bolts.
Grades 2 and 5, steel, and stainless steel, are the most prevalent types of carriage bolts. Common finishes for Grade 2 are zinc plating and hot dip galvanizing, and zinc plating for Grade 5.
A carriage bolt is a bolt with threading all the way up the shank to a small square shoulder, with a domed head. ... Once you seat the bolt through the hole, it is the job of the nut and washer to pull the bolt into the material tightly.
The strongest commercial-quality bolt is grade 8, marked by six raised dashes; its medium-carbon alloy steel has been quenched and tempered to achieve a tensile strength of 150,000 psi.