S-91257A803 5/8"-11 x 2 1/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 150,000 PSI ensures reliable performance in high-stress industrial applications, reducing the risk of fastener failure.
• Superior corrosion resistance from zinc yellow-chromate plating extends service life in harsh environments, minimizing maintenance and replacement costs.
• High hardness (Rockwell C33) provides excellent wear resistance and durability, maintaining thread integrity through repeated use.
• Coarse UNC threading allows for faster installation and easier alignment, saving time on assembly lines.
• Class 2A thread fit ensures consistent, reliable engagement with nuts and tapped holes, preventing cross-threading and ensuring secure connections.
• External hex drive design offers straightforward installation with common tools, improving efficiency in maintenance and production.
• Partial threading provides an unthreaded shank for enhanced shear strength, ideal for applications requiring precise clamping force.

Professional Applications & Engineering Value

This Grade 8 steel hex head screw is engineered to address critical challenges in heavy machinery, construction, and automotive assemblies where vibration, high loads, and environmental exposure are common. The zinc yellow-chromate plating delivers robust corrosion protection, significantly reducing degradation in moist or chemically aggressive settings. Its coarse UNC thread and partial threading design enhance grip and resistance to loosening under dynamic stresses, making it a reliable choice for structural frames, engine components, and industrial equipment. By combining 150,000 PSI tensile strength with precise Class 2A thread fit, this fastener ensures long-term reliability, minimizing downtime and maintenance in demanding B2B applications.

Specification Summary & Compliance

This hex head screw adheres to ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance consistency. Threads are manufactured to UNC coarse standards with a Class 2A fit for reliable engagement. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, guaranteeing environmental safety and regulatory adherence for global industrial use.