Glossary

A Grade 5 fastener is a medium-strength, heat-treated carbon steel bolt or screw defined by the SAE J429 standard. It represents the “general-purpose high-strength” category in the SAE grading system—stronger than Grade 2, but not as strong as Grade 8. Grade 5 is one of the most widely used fastener grades in North American industrial, automotive, and machinery applications.

Grade 5 bolts are typically made from medium-carbon steel (such as 1038, 1541, or similar steels) and are quenched and tempered to increase their tensile strength, hardness, and toughness. Their mechanical properties are significantly higher than Grade 2, with a minimum tensile strength of about 120,000 psi (for diameters up to 1 inch). This added strength makes them suitable for load-bearing assemblies, machinery, automotive components, agricultural equipment, heavy-duty brackets, structural joints, and general industrial equipment where durability and performance are essential.

Grade 5 fasteners are easy to identify: the head of a standard hex bolt will have three radial lines, evenly spaced, indicating its grade. They are often supplied in zinc-plated, plain/oil finish, or phosphate and oil variants. Because they offer an excellent balance of strength, cost, and availability, Grade 5 bolts are one of the most commonly stocked fastener grades in distribution, especially for MRO and OEM customers.