What are the differences in strength and application between SAE Grade 8 and ASTM A-490?

In some respects SAE J429 grade 8 bolts and ASTM A490 bolts are similar, and in other respects they are different. The first thing to address is the fact that these specifications are covered by different organizations. SAE (Society of Automotive Engineers) covers bolts for automotive, equipment, and OEM applications, whereas ASTM (American Society for Testing and Materials) covers fasteners for construction applications. By nature, SAE bolts are finished cap screws and are more precision fasteners than ASTM bolts.

Now let’s address the similarities. Both bolts have very similar chemical requirements (medium carbon alloy steel), strength properties (150ksi minimum tensile strength), and size range (maximum 1-1/2” diameter). The difference lies in the application and configuration of the fasteners. ASTM A490 bolts are a heavy hex head structural bolts designed for structural steel connections, while SAE J429 grade 8 bolts are finished cap screws with a standard size hex head and used in many equipment and automotive applications. Because A490 bolts are designed for structural connections, they will have a shorter thread length than grade 8 bolts.

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