S-91257A616 5/16"-24 x 3 1/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Load-Bearing Capability – With a 150,000 psi tensile strength and Rockwell C33 hardness, this screw withstands extreme forces, reducing the risk of failure in critical applications.
• Superior Corrosion Resistance – Zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh conditions.
• Reliable Thread Engagement – Fine UNF threading and Class 2A fit ensure precise, vibration-resistant connections, minimizing loosening in dynamic or high-stress environments.
• Optimized for Heavy-Duty Use – Grade 8 classification and partial threading design offer high clamp load capacity while reducing weight and material usage where full threads aren't needed.
• Easy Installation and Removal – External hex drive and standard 1/2" head width allow for quick, secure tool engagement with common wrenches, speeding up assembly and maintenance.
• Industry-Standard Compliance – Meets ASME B18.2.1 and SAE J429 specifications, ensuring interchangeability and performance reliability across industrial equipment and machinery.
• Environmental and Safety Assurance – RoHS 3 and REACH compliance guarantees that the fastener is free from hazardous substances, supporting sustainable and safe manufacturing practices.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address common challenges in heavy machinery, construction, and automotive sectors, where high tensile strength and corrosion resistance are paramount. The 5/16"-24 UNF fine thread and Class 2A fit provide superior vibration resistance, preventing joint failure in equipment subjected to constant motion or shock loads. The zinc yellow-chromate plating enhances durability in outdoor or chemically aggressive environments, reducing maintenance frequency and downtime. Partially threaded design concentrates strength where needed, making it ideal for securing structural components, engine parts, and industrial assemblies that demand reliable, long-term fastening without compromising on ASME B18.2.1 and SAE J429 standards. By integrating these features, the screw delivers consistent performance in heavy-duty applications, ensuring safety and efficiency in critical operations.

Specification Summary & Compliance

This fastener adheres to precise dimensional tolerances, including Class 2A thread fit for consistent engagement and UNF fine threading with 5/16"-24 size. It meets ASME B18.2.1 and SAE J429 manufacturing specifications for Grade 8 screws, ensuring mechanical properties like 150,000 psi tensile strength and Rockwell C33 hardness. Compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) confirms it is free from restricted substances, supporting environmental and safety standards in industrial supply chains.