S-91257A788 9/16"-18 x 6" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with a 150,000 psi tensile strength, ideal for high-stress structural and machinery applications.
• Superior corrosion resistance provided by the zinc yellow-chromate plating, extending service life in harsh industrial environments.
• Reliable fine thread engagement with 9/16"-18 UNF Class 2A threads, ensuring precise, vibration-resistant connections.
• High-grade material integrity from Grade 8 steel and Rockwell C33 hardness, offering excellent durability and wear resistance.
• Optimized for high-torque installation thanks to the external hex drive and 13/16" head width, allowing for secure tightening.
• Versatile partial threading design provides strong grip on thick materials while facilitating alignment during assembly.
• Compliance with major industry standards including ASME B18.2.1 and SAE J429, guaranteeing consistent quality and performance.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address critical challenges in heavy machinery, construction, and automotive assemblies where joint integrity is paramount. The 9/16"-18 UNF fine threading and Class 2A thread fit deliver superior resistance to loosening under dynamic loads and vibrations, a common failure point in industrial equipment. Manufactured from high-strength steel and finished with zinc yellow-chromate plating, it combats corrosion in outdoor or chemically aggressive settings, reducing maintenance frequency. The partially threaded shank ensures that the unthreaded portion bears against materials to prevent shear, while the threaded section secures the nut or tapped hole effectively. These features make it an indispensable high-strength fastener for demanding applications such as structural frames, engine components, and heavy-duty manufacturing fixtures.

Specification Summary & Compliance

This fastener adheres to precise dimensional and performance criteria, including a Class 2A thread fit for consistent assembly and UNF fine thread specifications. It is manufactured in compliance with ASME B18.2.1 and SAE J429 standards, ensuring reliability across industrial uses. Additionally, the product is confirmed to be RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting stringent environmental and safety regulations for global supply chains.