S-91257A878 3/4"-16 x 3 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 with Grade 8 classification and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Precise thread engagement with Class 2A thread fit and UNF fine threading for vibration-resistant connections
• Optimized torque transmission through external hex drive and 1 1/8" head width for secure installation
• Enhanced durability with Rockwell C33 hardness that maintains performance under repeated stress
• Versatile partial threading design allowing both clamping and alignment functions in heavy assemblies
• Full regulatory compliance meeting ASME B18.2.1, SAE J429, RoHS 3, and REACH standards for global applications

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver exceptional engineering value in demanding industrial applications where failure is not an option. The 3/4"-16 UNF fine threading provides superior resistance to vibration loosening compared to coarse threads, making them ideal for machinery, heavy equipment, and structural assemblies subject to dynamic loads. The zinc yellow-chromate plating creates a robust barrier against corrosion while maintaining electrical conductivity for grounding applications. With partial threading and substantial 3 1/2" length, these fasteners efficiently distribute clamping forces across joined materials while allowing unthreaded sections to serve as precision alignment pins. The external hex drive and generous head dimensions enable high-torque installation without stripping, ensuring reliable performance in maintenance-critical operations.

Specification Summary & Compliance

Manufactured to exacting ASME B18.2.1 and SAE J429 specifications, these inch-system fasteners feature Class 2A thread fit tolerances for consistent engagement. The 3/4"-16 UNF threading maintains precise fine thread spacing with minimum 1 3/4" threaded length. Full compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations ensures environmental responsibility while the Grade 8 certification guarantees mechanical properties including 150,000 psi tensile strength and Rockwell C33 hardness are consistently maintained.