S-91257A557 1/4"-20 x 3 3/4" 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 Grade 8 strength rating and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Optimized thread engagement with Class 2A UNC coarse threads ensuring reliable installation and vibration resistance
• Enhanced torque transmission via external hex drive design that prevents tool slippage during high-torque applications
• Precision dimensional control meeting ASME B18.2.1 and SAE J429 specifications for consistent performance
• Reduced installation time with partially threaded design that allows for faster assembly in specific mounting scenarios
• Regulatory compliance assurance with RoHS 3 and REACH environmental standards for global market acceptance

Professional Applications & Engineering Value

Engineered for demanding industrial applications, these Grade 8 hex head screws deliver exceptional performance in construction, heavy machinery, and structural assemblies where high tensile strength and reliable fastening are critical. The zinc yellow-chromate plating provides superior corrosion resistance, extending service life in outdoor or chemically aggressive environments. With UNC coarse threads and Class 2A thread fit, these screws offer excellent engagement in various materials while resisting vibration-induced loosening. The partially threaded design allows for precise clamping force distribution, making them ideal for applications requiring specific grip lengths. These industrial-grade fasteners maintain integrity under extreme loads, ensuring long-term reliability in critical connections.

Specification Summary & Compliance

This 1/4"-20 x 3 3/4" hex head screw features Class 2A thread fit with UNC coarse threads and partial threading up to 3/4" minimum thread length. Manufactured to ASME B18.2.1 and SAE J429 Grade 8 specifications, it delivers consistent dimensional accuracy and mechanical properties. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use across global markets while maintaining the highest industry standards for quality and performance.