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.
Strength Differences
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.
Configuration Differences
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″.
Engineering student here working on a senior design project, what is the elastic modulus of a Grade 8 bolt? Thanks!
@JBrucki- We are sorry, but that isn’t information we have. SAE grade 8 bolts are tested for tensile, yield, ductility, etc but the modulus is not reported or saved by our software.
Hello,
I would like to know is that grade 8 pins are good for shear and shocks at the same time
It is for the installation of piles
Thank you
@Abdel- SAE grade 8 pins are quite high in strength, but we are unable to make any specific applications recommendations.
Hello! Is ASTM4140 Bolt equivalent with A325 bolt?
@Seiji- 4140 is not an ASTM standard, it is a chemical only call-out governed by AISI and is for raw steel only, not finished fasteners. A325 is a finished bolt standard that can be made from many different types of steel. You will have to look at the MTRs and make sure that your 4140 conforms to the A325 chemical requirements. Heat treatment and testing will also be required in order to achieve the needed mechanical requirements.
If we require a a307 bolt but what we have given to us is an AISI 1020 bolt, will it suffice our requirement? Thanks
@Rechelle- It might. A307 has some chemical and mechanical requirements that might be met by AISI 1020, but you’d have to look at the testing paperwork to see if it meets. Without that, you couldn’t definitively tell one way or the other.