S-91286A385 1/2"-20 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 and Rockwell C33 hardness for reliable performance in high-stress industrial applications.
• Superior corrosion resistance provided by the zinc-flake coating, extending service life in harsh environments and reducing maintenance costs.
• Precise thread engagement with Class 2A fit and 1/2"-20 UNF fine threads, ensuring secure fastening and vibration resistance.
• Optimized torque transmission through the external hex drive and 3/4" head width, allowing for easy installation with standard tools.
• Reduced assembly weight and material use with the partially threaded design, while maintaining a minimum 1-1/4" thread length for sufficient grip.
• Compliance with major industry standards including ASME B18.2.1 and SAE J429, guaranteeing interchangeability and quality assurance.
• Environmental regulation adherence with RoHS 3 and REACH compliance, ensuring safe use in regulated markets and sustainable sourcing.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address critical challenges in heavy machinery, construction, and automotive assemblies where high tensile strength and corrosion resistance are paramount. The zinc-flake coated steel construction provides a durable barrier against rust and chemical exposure, significantly reducing failure risks in outdoor or corrosive settings. Its 1/2"-20 UNF fine thread and Class 2A thread fit deliver precise alignment and enhanced clamping force, minimizing loosening under dynamic loads. The partially threaded shank concentrates stress appropriately, making it ideal for bolting flanges, brackets, and structural frames that demand reliable, long-term fastening solutions without compromising on industrial safety standards.

Specification Summary & Compliance

This screw adheres to Class 2A thread fit tolerances and UNF (Unified National Fine) thread standards, ensuring dimensional accuracy and compatibility. It meets ASME B18.2.1 and SAE J429 specifications for hex head fasteners, confirming consistent manufacturing quality. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, supporting environmentally responsible procurement and use in global markets.