S-91257A449 5/16"-24 x 6" 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 Grade 8 classification and 150,000 psi tensile strength for reliable performance in high-stress environments.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh industrial conditions.
• Precise thread engagement with UNF fine threads and Class 2A fit ensuring secure, vibration-resistant connections.
• Optimized torque transmission through the external hex drive and 1/2" head width for easy installation with standard tools.
• Enhanced durability from Rockwell C33 hardness, maintaining structural integrity under repeated mechanical stress.
• Versatile partial threading allowing unthreaded shank sections for shear strength while maintaining full thread engagement where needed.
• Regulatory compliance assurance meeting ASME B18.2.1, SAE J429, RoHS 3, and REACH standards for global industrial applications.

Professional Applications & Engineering Value

This Grade 8 hex head screw delivers critical engineering solutions for heavy machinery, structural assemblies, and equipment requiring high-strength fastening. The steel construction with Rockwell C33 hardness provides exceptional resistance to deformation under extreme loads, while the zinc yellow-chromate plating creates a protective barrier against oxidation and chemical exposure in demanding environments. The UNF fine thread configuration offers superior vibration resistance compared to coarse threads, maintaining clamp force in dynamic applications. With partial threading and 6" length, this fastener optimally distributes stress across both threaded and unthreaded sections, preventing thread stripping in soft materials while providing maximum shear strength. These characteristics make it ideal for construction equipment, automotive systems, and industrial machinery where reliable performance and long-term durability are paramount.

Specification Summary & Compliance

This fastener maintains Class 2A thread fit tolerance for consistent engagement and meets ASME B18.2.1 dimensional specifications under SAE J429 standards. Manufacturing complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental responsibility. The 5/16"-24 UNF fine thread provides precise pitch control with 0.3125" diameter and minimum 7/8" thread length on the 6" overall fastener, delivering reliable performance across industrial applications.