S-91286A451 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 a tensile strength of 150,000 PSI and Rockwell C33 hardness, this screw reliably handles extreme stress and vibration in demanding applications.
• Superior Corrosion Defense: The Zinc-Flake coating provides a robust barrier against rust and corrosion, significantly extending the service life of assemblies in harsh environments.
• Precise & Secure Fastening: The Class 2A thread fit and UNF fine thread design ensure consistent, tight engagement and reduced risk of loosening under dynamic loads.
• Optimized for High-Torque Applications: The large 15/16" external hex head offers excellent grip for powerful wrenching, facilitating easier installation and removal.
• Enhanced Joint Stability: The partially threaded shank allows for an unthreaded section to bear directly against materials, providing superior clamp force and shear resistance.
• Guaranteed Reliability & Traceability: Manufactured to meet ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and consistent performance.
• Safe for Regulated Industries: Compliant with RoHS 3 and REACH standards, making it suitable for use in environmentally conscious and globally regulated markets.

Professional Applications & Engineering Value

This Grade 8 Hex Head Screw is engineered to solve critical challenges in heavy-duty industrial applications. Its high-strength steel construction and 150,000 PSI tensile strength make it ideal for structural frameworks, heavy machinery, and high-vibration equipment where fastener failure is not an option. The Zinc-Flake coating directly addresses the common industrial pain point of corrosion in outdoor or chemically aggressive environments, drastically reducing maintenance cycles and replacement costs. The combination of a fine UNF thread and Class 2A fit provides a precise, leak-resistant seal in pressurized assemblies, while the external hex drive and 4" length offer the versatility needed for both thick and complex assemblies. This fastener delivers predictable, reliable performance that engineers and procurement specialists can depend on for critical connections.

Specification Summary & Compliance

This screw adheres to strict dimensional standards with a Class 2A thread fit and UNF (Unified National Fine) 5/8"-18 threading. It is manufactured in accordance with ASME B18.2.1 and meets the material and mechanical requirements of SAE J429 for Grade 8. The product is confirmed to be RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, ensuring it is free of restricted hazardous substances and safe for use in various international markets.