S-91257A599 5/16"-18 x 3 3/4" 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 150,000 psi tensile strength for reliable performance in high-stress applications
• Superior corrosion protection through zinc yellow-chromate plating that extends service life in harsh environments
• Optimized torque transmission with external hex drive design ensuring secure installation and removal
• Enhanced thread engagement through Class 2A thread fit providing consistent clamping force
• Reduced cross-threading risk with UNC coarse threading for faster assembly in industrial settings
• Precise unthreaded shank section allowing for better shear strength distribution in structural connections
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed interoperability

Professional Applications & Engineering Value

Engineered for demanding industrial applications, these Grade 8 hex head screws deliver exceptional performance in construction, heavy machinery, and structural steel connections. The partially threaded design provides an unthreaded bearing surface that prevents joint loosening under vibration while maintaining superior shear strength. The zinc yellow-chromate plated finish creates a protective barrier against corrosion in outdoor or chemically aggressive environments. With 5/16"-18 UNC coarse threading, these fasteners enable rapid installation in structural steel, equipment frames, and load-bearing assemblies where high-strength fastening is critical. The external hex drive accommodates standard tools for efficient maintenance and disassembly in industrial settings.

Specification Summary & Compliance

Manufactured to precise dimensional standards with Class 2A thread fit and UNC coarse thread spacing ensuring consistent performance across applications. These hex head screws comply with ASME B18.2.1 and SAE J429 specifications for dimensional accuracy and mechanical properties. The fasteners are fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, containing no restricted substances. With Rockwell C33 hardness and verified 150,000 psi tensile strength, these screws meet the rigorous requirements for Grade 8 heavy-duty fasteners in critical applications.