The ASTM A307 specification covers carbon steel bolts and studs ranging from 1/4″ through 4″ diameter. This is your everyday, run of the mill bolt specification often manufactured using A36 round bar. There are three grades A, B, and C* which denote tensile strength, configuration, and application. Refer to the Mechanical Properties Chart for the subtle strength differences within each grade.

ASTM A307 Grades

307A		Headed bolts, threaded rods and bent bolts intended for general applications.
307B		Heavy hex bolts and studs intended for flanged joints in piping systems with cast iron flanges.
307C		Non-headed anchor bolts, either bent or straight, intended for structural anchorage purposes. The end of a grade C anchor bolt intended to project from the concrete will be painted green for identification purposes. Permanent marking is a supplemental requirement.

*As of August 2007, grade C has been replaced by specification F1554 grade 36.