S-91257A829 5/8"-18 x 4" 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 withstands harsh industrial environments
• Precise thread engagement with Class 2A thread fit ensuring consistent, vibration-resistant connections
• Enhanced durability from Rockwell C33 hardness that maintains structural integrity under repeated stress
• Optimized torque transmission via external hex drive design for efficient installation and removal
• Fine thread spacing advantage providing better adjustment precision and superior clamping force distribution
• Regulatory compliance assurance meeting ASME B18.2.1, SAE J429, RoHS 3, and REACH standards for quality and safety

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical engineering solutions for heavy machinery, structural assemblies, and industrial equipment where failure is not an option. The 5/8"-18 UNF fine threading combined with Class 2A thread fit ensures precise engagement in tapped holes, reducing the risk of cross-threading while maintaining vibration resistance in dynamic applications. The zinc yellow-chromate plating provides a dual-layer protective barrier against corrosion, extending service life in challenging environments. With partial threading design, these fasteners offer optimal grip length for thick materials while minimizing thread damage during repeated disassembly. The external hex drive configuration allows for high-torque installation using standard tools, making them ideal for maintenance operations and production line applications where reliability and quick assembly are paramount.

Specification Summary & Compliance

This 4" length hex head screw features precise Class 2A thread fit with 5/8"-18 UNF fine threading and right-hand thread direction. 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 various industrial sectors while maintaining the highest quality standards for professional applications.