S-91257A749 1/2"-20 x 2 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 for critical structural applications
• Superior corrosion resistance through zinc yellow-chromate plating in harsh industrial environments
• Enhanced durability with Rockwell C33 hardness to withstand repeated stress and vibration
• Precise thread engagement with Class 2A UNF fine threads for secure, vibration-resistant connections
• Easy installation and removal using standard tools with external hex drive design
• Optimized thread distribution through partial threading for balanced strength and weight efficiency
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for reliable performance

Professional Applications & Engineering Value

This Grade 8 hex head screw delivers exceptional engineering value for heavy-duty industrial applications where failure is not an option. The UNF fine thread configuration provides superior resistance to vibration loosening in machinery, automotive assemblies, and structural frameworks. The zinc yellow-chromate plating creates a protective barrier against corrosion in demanding environments, extending service life while maintaining electrical conductivity. With partial threading optimizing the strength-to-weight ratio, this fastener is ideal for applications requiring precise clamp load distribution. The external hex drive ensures reliable torque application during installation, while the 1/2"-20 thread size offers excellent holding power in high-stress connections. Engineered to withstand extreme conditions, this screw provides dependable performance in construction equipment, industrial machinery, and transportation applications where 150,000 psi tensile strength is critical for safety and reliability.

Specification Summary & Compliance

This hex head screw features precision Class 2A thread fit with 1/2"-20 UNF fine threads and 2 1/4" length. Manufactured to ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and mechanical properties. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, making it suitable for global industrial applications requiring strict chemical substance control.