S-91257A811 5/8"-11 x 3 1/4" 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 Grade 8 rating and 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 industrial environments
• Optimized torque transmission with external hex drive design ensuring secure installation and removal with standard tools
• Precise thread engagement with Class 2A thread fit and UNC coarse threading for faster assembly and reduced cross-threading risks
• Enhanced durability from Rockwell C33 hardness that maintains structural integrity under repeated stress and vibration
• Versatile partial threading allowing unthreaded shank sections to bear against materials while threaded portions provide secure fastening
• Regulatory compliance assurance meeting ASME, SAE, RoHS 3, and REACH standards for quality and environmental safety

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical performance where structural integrity cannot be compromised. The 150,000 psi tensile strength and Rockwell C33 hardness make them ideal for heavy machinery, construction equipment, and industrial assemblies subjected to extreme loads and vibrations. The zinc yellow-chromate plating provides a robust barrier against corrosion in outdoor or chemically aggressive environments, significantly extending maintenance intervals. With UNC coarse threading and Class 2A thread fit, these screws offer faster installation in steel frameworks and structural connections while minimizing the risk of thread damage. The partial threading design allows the unthreaded shank to carry shear loads effectively, making these 5/8"-11 hex screws essential for critical bolted joints in manufacturing, infrastructure, and heavy equipment applications.

Specification Summary & Compliance

This 5/8"-11 UNC hex head screw features precise Class 2A thread fit tolerance with coarse threading for optimal engagement. Manufacturing complies with ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and mechanical properties. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, containing no restricted substances. With 3 1/4" length and partial threading (minimum 1 1/2" thread length), these screws maintain consistent performance across industrial applications requiring high-strength fastening solutions.