S-91257A921 7/8"-9 x 5" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capacity with 150,000 psi tensile strength and Rockwell C33 hardness for reliable performance in high-stress applications
• Superior corrosion resistance through zinc yellow-chromate plating that extends service life in harsh industrial environments
• Optimized thread engagement with coarse UNC threading and Class 2A fit ensuring secure fastening and vibration resistance
• Enhanced installation efficiency featuring external hex drive and standard hex head for easy tool access and high torque application
• Partial threading design providing unthreaded shank section for precise clamping force distribution
• Heavy-duty construction meeting Grade 8 specifications for the most demanding mechanical and structural applications
• Regulatory compliance assurance with RoHS 3 and REACH standards for environmental safety and global market acceptance

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws deliver exceptional performance in construction equipment, machinery assembly, and structural steel connections. The 7/8"-9 UNC coarse thread configuration provides superior resistance to vibration loosening while enabling faster installation compared to fine-thread alternatives. The zinc yellow-chromate plating creates a robust barrier against corrosion, significantly extending service life in outdoor or chemically aggressive environments. With partial threading design, these fasteners concentrate clamping force precisely where needed, preventing joint failure in critical assemblies. The combination of 150,000 psi tensile strength and Rockwell C33 hardness ensures reliable performance under extreme mechanical stress, making them ideal for high-load bolting applications where failure is not an option.

Specification Summary & Compliance

This heavy-duty hex head screw features precise Class 2A thread fit with 7/8"-9 UNC coarse threading and 5" length with minimum 2" thread length. Manufactured from high-strength steel with external hex drive and 37/64" head height by 1 5/16" head width. Complies with ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental compliance standards for safe industrial use.