A307 is a specification that covers carbon steel fasteners ranging from 1/4” through 4” in diameter. This is a generic, everyday bolt specification that is typically manufactured from A36 round bar. It is widely available in imported material, has limited availability domestically manufactured, and can also be custom manufactured in nonstandard sizes.


There are two current grades and one withdrawn grade under the A307 specification. Each grade has specific application and configuration limitations. A307 grade C was replaced in August of 2007 by the F1554 Grade 36 anchor bolt specification. However, it can still be manufactured if required by the project.

A ASTM A307 Grade A Headed bolts, threaded rods and bent bolts intended for general applications.
B ASTM A307 Grade B Heavy hex bolts and studs intended for flanged joints in piping systems with cast iron flanges.
C* ASTM A307 Grade C Nonheaded 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 *As of August 2007, grade C has been replaced by specification F1554 grade 36. We will continue to supply grade C, if required by the project.

A307 Grade A is used for general purpose applications and has no configuration limitations and can be made in any form (straight rod, bent, or headed). A307 Grade B is a heavy hex bolt or fully threaded stud designed to be used in cast iron flange connections. A307 Grade C, when it existed, was designed for bent or straight threaded anchor bolts.

The marking requirements for grades A and B are a manufacturer’s logo (PB) followed by the grade marking as shown in the table above. Grade C anchor bolts were color-coded green on the end projecting from the concrete, and a permanent mark was a supplemental requirement that needed to be specified.


A307 fasteners are available primarily in three finishes. The first is plain or uncoated steel which will be susceptible to rust if exposed to the natural elements. The second is hot-dip galvanized per ASTM F2329. The third common finish is zinc plated per ASTM F1941. Other less-common coatings such as cadmium plated and black oxide are available as a special order.