S-91257A574 1/4"-28 x 3 1/4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum Load-Bearing Capacity with 150,000 psi tensile strength and Grade 8 classification for reliable performance in high-stress applications
• Superior Corrosion Resistance through zinc yellow-chromate plating that protects against rust and extends service life in harsh environments
• Enhanced Durability featuring Rockwell C33 hardness for excellent wear resistance and long-term fastener integrity
• Precise Fastening Control with 1/4"-28 UNF fine threads and Class 2A fit ensuring secure, vibration-resistant connections
• Optimized Installation Efficiency through external hex drive design that allows for high-torque application with standard tools
• Versatile Application Design with partial threading that provides both threaded engagement and smooth shank benefits
• Industry Compliance Assurance meeting ASME B18.2.1 and SAE J429 specifications for quality and interoperability

Professional Applications & Engineering Value

This Grade 8 hex head screw delivers exceptional engineering value for industrial applications where failure is not an option. The steel construction with Rockwell C33 hardness provides the structural integrity needed for heavy machinery, construction equipment, and automotive assemblies. The 1/4"-28 UNF fine thread configuration offers superior resistance to vibration loosening compared to coarse threads, while the partial threading design allows for precise clamp load distribution. The zinc yellow-chromate plating creates a protective barrier against corrosion in demanding environments, from manufacturing facilities to outdoor installations. With external hex drive compatibility, installers can achieve proper preload using standard tools, reducing installation time and ensuring consistent performance across multiple fastening points in critical assemblies.

Specification Summary & Compliance

This heavy-duty fastener features precision Class 2A thread fit with 1/4"-28 UNF fine threads and right-hand direction. The 3 1/4" length includes 3/4" minimum thread length for optimal engagement. Manufactured to exacting ASME B18.2.1 and SAE J429 specifications, this Grade 8 hex head screw maintains dimensional accuracy and mechanical properties required for industrial applications. The zinc yellow-chromate finish provides corrosion protection while maintaining compliance with industry standards for high-strength fasteners.