S-91257A879 3/4"-16 x 4 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capability with Grade 8 strength and 150,000 psi tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Precise thread engagement with Class 2A UNF fine threads ensuring reliable fastening in high-vibration settings
• Optimized torque transmission via external hex drive and 1 1/8" head width for efficient installation with standard tools
• Enhanced durability from Rockwell C33 hardness that maintains fastener integrity under repeated stress
• Versatile partial threading allowing both clamping and alignment functions in complex assemblies
• Regulatory compliance assurance meeting ASME B18.2.1, RoHS 3, and REACH standards for global project acceptance

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws solve critical fastening challenges in construction machinery, structural steel connections, and high-stress equipment assemblies. The 3/4"-16 UNF fine threading provides superior resistance to vibrational loosening compared to coarse threads, while the zinc yellow-chromate plating creates a protective barrier against corrosion in outdoor or chemically aggressive environments. The partially threaded design allows the unthreaded shank to bear shear loads directly, preventing thread damage in bolted joints subject to lateral forces. With 150,000 psi tensile strength and Rockwell C33 hardness, these fasteners maintain clamping force under extreme conditions where ordinary bolts would fail, making them ideal for critical connections in industrial machinery, transportation equipment, and infrastructure projects requiring long-term reliability and consistent performance.

Specification Summary & Compliance

This 4 1/2" length hex head screw features Class 2A thread fit per UNF standards with 1 3/4" minimum thread length and precise dimensional compliance with ASME B18.2.1 specifications (SAE J429). The fastener meets RoHS 3 (2015/863/EU) compliance for restricted substances and REACH (EC 1907/2006) regulations regarding chemical safety. Manufacturing follows Grade 8 strength classification requirements with verified 150,000 psi tensile strength and Rockwell C33 hardness testing to ensure consistent performance across production batches.