Is a Grade 8 bolt the same as an ASTM A325?
ASTM A325 and SAE J429 grade 8 are not the same fastener. As a matter of fact, they couldn’t be more different. SAE (Society of Automotive Engineers) establishes specifications covering fasteners intended for use in automotive, OEM, and equipment applications, while ASTM (American Society for Testing and Materials) provides specifications for construction fasteners. There are several differences between these two bolts, including chemistry, strength, application, and dimensional tolerances.
A325 bolts are typically manufactured from a medium carbon steel (although they can be made from an alloy) while SAE grade 8 bolts are made from a medium carbon alloy steel. Grade 8 bolts are significantly stronger than an A325. An ASTM specification with similar strength properties to grade 8 is ASTM A490.
|Grade||Nominal Size||Proof Load Min (ksi)||Yield Strength Min (ksi)||Tensile Strength Min (ksi)||Rockwell Hardness Min||Rockwell Hardness Max|
|ASTM A325-1||1/2" - 1"||85||92||120||C24||C35|
|1-1/8" - 1-1/2"||74||81||105||C19||C31|
|SAE J429 Grade 8||1/4" - 1-1/2"||120||130||150||C33||C39|
Compare more strengths with our strength by grade chart.
ASTM A325 bolts are heavy hex structural bolts and used in structural steel connections, while SAE grade 8 bolts are finished hex bolts and typically used in automotive and equipment applications. By nature, an SAE bolt is also a more precision fastener with tighter tolerances than an ASTM bolt.
Mechanical properties for A325 bolts under the new F3125 specification are the same for all diameters. Under the original A325 specification, mechanical requirements change for diameters above 1″.