S-91247A449 5/8"-18 x 5 1/2" ASME B18.2.1, SAE J429 Medium-Strength Grade 5 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with Grade 5 classification and 120,000 psi tensile strength for demanding industrial applications
• Superior corrosion resistance through zinc plating that extends service life in harsh environments
• Precise thread engagement with UNF fine threading and Class 2A fit ensuring reliable fastening performance
• Optimized torque transmission through external hex drive design that prevents tool slippage during installation
• Enhanced durability with Rockwell C25 hardness rating that maintains structural integrity under stress
• Versatile partial threading design allowing both secure clamping and clearance functions in assemblies
• Regulatory compliance assurance meeting ASME B18.2.1 standards for consistent quality and performance

Professional Applications & Engineering Value

This Grade 5 hex head screw delivers critical performance in heavy machinery, structural steel connections, and industrial equipment assemblies where vibration resistance and high tensile strength are paramount. The 5/8"-18 UNF fine threading provides superior resistance to loosening under dynamic loads compared to coarse threads, while the zinc plated finish creates a protective barrier against corrosion in manufacturing environments. The partially threaded design allows the unthreaded shank to bear shear loads efficiently while the threaded portion secures components. With external hex drive compatibility, installation torque is effectively transferred without cam-out issues, making these fasteners ideal for construction, automotive, and industrial maintenance applications requiring reliable, high-strength fastening solutions.

Specification Summary & Compliance

Manufactured to ASME B18.2.1 specifications and SAE J429 Grade 5 standards, this hex head screw features precise Class 2A thread fit tolerances for consistent engagement. The fastener maintains compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring suitability for global industrial applications. With 5/8"-18 UNF fine threading and 5-1/2" length, this partially threaded screw delivers reliable performance where high-strength fastening and corrosion resistance are required.