S-91257A193 5/8"-18 x 6 1/2" 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 and Rockwell C33 hardness for reliable performance in high-stress applications
• Superior corrosion resistance through zinc yellow-chromate plating that protects against rust and environmental degradation
• Precise thread engagement with Class 2A UNF fine threads ensuring secure fastening and vibration resistance
• Optimized torque transmission via external hex drive design that prevents tool slippage during installation
• Reduced assembly weight through partial threading while maintaining full structural integrity where needed
• Industry-standard compatibility meeting ASME B18.2.1 and SAE J429 specifications for guaranteed interchangeability
• Enhanced installation efficiency with standard 15/16" hex head allowing use with common industrial tools

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical performance in demanding industrial environments where fastener failure is not an option. The 150,000 psi tensile strength and Rockwell C33 hardness provide exceptional resistance to shear and tensile forces in heavy machinery, structural steel connections, and high-vibration equipment. The zinc yellow-chromate plating creates a protective barrier against corrosion in outdoor applications or harsh chemical environments. With 5/8"-18 UNF fine threading and Class 2A thread fit, these screws maintain precise clamping force while the partial threading design optimizes weight distribution. The external hex drive configuration ensures reliable torque application without cam-out, making them ideal for construction equipment, industrial machinery, and transportation applications requiring ASME B18.2.1 compliant fasteners.

Specification Summary & Compliance

Manufactured to exacting inch system dimensions with Class 2A thread fit tolerance per UNF standards. These steel fasteners feature 5/8"-18 UNF fine threads with minimum thread length of 1-3/4" on a 6-1/2" overall length. Fully compliant with ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring mechanical properties and dimensional accuracy for industrial applications. The zinc yellow-chromate plating provides corrosion protection while maintaining RoHS and REACH compliance for environmental safety.