S-91257A593 5/16"-18 x 2 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum Load-Bearing Capacity – Grade 8 steel construction and 150,000 psi tensile strength ensure reliable performance in high-stress industrial environments.
• Superior Corrosion Resistance – Zinc yellow-chromate plating provides long-lasting protection against rust and environmental degradation.
• Optimized Thread Engagement – UNC coarse thread spacing and Class 2A thread fit enable quick assembly and secure fastening in various materials.
• High Durability Under Stress – Rockwell C33 hardness and partially threaded design reduce the risk of shear failure and thread stripping.
• Easy Installation and Removal – External hex drive and 1/2" head width allow for standard wrench access and high-torque application.
• Compliance with Industry Standards – Meets ASME B18.2.1 and SAE J429 specifications, ensuring consistent quality and interchangeability.
• Environmentally Responsible Manufacturing – RoHS 3 and REACH compliance supports sustainable procurement and safe usage in regulated industries.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered for heavy-duty applications where structural integrity and corrosion resistance are critical. The zinc yellow-chromate plating offers enhanced protection in harsh environments, such as outdoor machinery, construction equipment, and automotive assemblies. Its UNC coarse thread and Class 2A fit provide reliable grip in both metal and composite materials, reducing the likelihood of loosening under vibration. The partially threaded shank concentrates strength where needed, making it ideal for bolting joints that require precise clamping force without compromising the fastener’s endurance. Whether used in manufacturing, infrastructure, or transport sectors, this screw delivers consistent performance backed by ASME B18.2.1 and SAE J429 standards.

Specification Summary & Compliance

This fastener adheres to Class 2A thread tolerance and UNC coarse thread specifications, with a thread size of 5/16"-18 and a minimum thread length of 7/8". It conforms to ASME B18.2.1 and SAE J429 manufacturing standards, ensuring dimensional accuracy and mechanical reliability. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for use in environmentally conscious and regulated industrial markets.