S-91257A758 1/2"-20 x 5 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 for reliable performance in high-stress applications
• Superior corrosion resistance through zinc yellow-chromate plating that protects against harsh industrial environments
• Precise thread engagement with Class 2A thread fit ensuring consistent mating 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 1¼" minimum thread length for secure fastening
• Enhanced durability with Rockwell C33 hardness providing excellent wear resistance and longevity
• Regulatory compliance assurance meeting ASME B18.2.1 standards and environmental regulations for global industrial use

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical engineering solutions for heavy machinery, structural assemblies, and industrial equipment where high tensile strength and corrosion resistance are paramount. The 1/2"-20 UNF fine threading provides superior vibration resistance in dynamic applications, while the zinc yellow-chromate plating creates a protective barrier against moisture, chemicals, and environmental degradation. The external hex drive design enables high-torque installation without cam-out, making these partially threaded screws ideal for applications requiring precise clamp load distribution. Engineered to withstand extreme conditions, these fasteners prevent joint failure in construction, automotive, and manufacturing sectors where reliability cannot be compromised.

Specification Summary & Compliance

Manufactured to exacting Class 2A thread fit tolerances with UNF thread form specifications, these hex head screws comply with ASME B18.2.1 dimensional standards and SAE J429 Grade 8 mechanical properties. The fasteners are fully RoHS 3 (2015/863/EU) compliant and meet REACH (EC 1907/2006) environmental regulations, ensuring they can be used in global industrial applications without restriction. With precise 5½" length and 1¼" minimum thread length, these components deliver consistent performance across demanding applications.