S-91247A408 9/16"-18 x 2 3/4" ASME B18.2.1, SAE J429 Medium-Strength Grade 5 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Enhanced load-bearing capacity with 120,000 PSI tensile strength for reliable performance in high-stress applications
• Superior corrosion resistance through zinc plating, extending service life in demanding industrial environments
• Precise thread engagement with Class 2A fit and UNF fine threading for secure fastening and vibration resistance
• Optimized torque transmission via external hex drive and 13/16" head width for efficient installation with standard tools
• Controlled thread engagement through partial threading design, preventing over-tightening in specific assembly scenarios
• Consistent mechanical properties with Rockwell C25 hardness ensuring dimensional stability under load
• Regulatory compliance assurance meeting both industry standards and environmental regulations for global applications

Professional Applications & Engineering Value

This Grade 5 steel hex head screw delivers exceptional engineering value through its balanced combination of high tensile strength and controlled hardness. The 9/16"-18 UNF fine threading provides superior resistance to vibrational loosening in heavy machinery, automotive assemblies, and structural frameworks where dynamic loads are present. The zinc plated finish actively protects against corrosion in industrial atmospheres, while the partially threaded design allows for precise clamp load distribution in multi-material assemblies. Engineers specify this external hex drive fastener for applications requiring reliable disassembly and reassembly cycles, supported by the robust 13/16" head width that withstands high torque applications without stripping. The combination of ASME B18.2.1 compliance and fine thread configuration makes it particularly valuable for precision equipment where thread engagement control is critical to performance.

Specification Summary & Compliance

This hex head screw maintains precise Class 2A thread fit tolerances according to UNF standards, ensuring consistent engagement across applications. Manufacturing follows ASME B18.2.1 specifications where identified under SAE J429, guaranteeing dimensional accuracy and mechanical properties. The fastener demonstrates full compliance with RoHS 3 (2015/863/EU) restrictions on hazardous substances and REACH (EC 1907/2006) regulations regarding chemical safety. With Grade 5 classification confirming 120,000 PSI tensile strength and Rockwell C25 hardness, this screw meets rigorous industrial requirements for heavy-duty fastening applications.