ASTM and SAE Differences

There are two specifying bodies when it comes to fasteners. ASTM (American Society for Testing and Materials) covers primarily bolts and fasteners for construction applications. SAE (Society of Automotive Engineers) covers fasteners for automotive, machinery, and OEM applications.

ASTM A307 grade B is made from a low carbon steel and is a relatively low strength heavy hex bolt or stud specifically intended for cast iron pipe flange connections. ASTM A449 is a medium carbon steel that is heat treated to develop higher strength characteristics than A307 grade B. Whereas A307 grade B is limited by its configuration (heavy hex head bolt or stud) and its application (cast iron flange connections), A449 can be used for general applications and is unlimited in its configuration. In other words, an A449 bolt can be any type of headed bolt, any shape of bent bolt, or straight rods that are fully threaded, have threads on both ends, or have thread on one end only. Grade 5 bolts are covered under SAE guidelines and by nature are a more precision fastener than ASTM bolts. They are virtually identical to ASTM A449 in chemistry and strength, but max out at 1-1/2″ diameter while A449 bolts extend to 3″ diameter.