S-91257A753 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

• Maximum Load-Bearing Capacity: With a tensile strength of 150,000 psi and Rockwell C33 hardness, this screw withstands extreme stress and vibration, reducing the risk of failure in critical assemblies.
• Superior Corrosion Resistance: The zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh industrial settings.
• Precise, Secure Fastening: Class 2A thread fit and UNF fine thread design ensure tight, reliable engagement with minimal risk of loosening under dynamic loads.
• High-Strength Material Integrity: Manufactured from Grade 8 steel, this fastener meets rigorous SAE J429 standards, offering consistent performance for heavy-duty applications.
• Optimized for High-Torque Applications: The external hex drive and 3/4" head width allow for easy installation with standard tools, even in high-torque scenarios.
• Versatile Threading Design: Partially threaded shank provides unthreaded grip length for enhanced clamping force where needed, improving joint stability.
• Regulatory Compliance Assurance: Compliant with RoHS 3, REACH, and ASME B18.2.1, ensuring safety and environmental standards are met for global supply chains.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address common industrial challenges such as joint failure under high stress and corrosion in demanding environments. The 1/2"-20 UNF fine thread and Class 2A thread fit deliver precise alignment and superior clamping force, minimizing loosening in machinery, structural steel connections, and heavy equipment. The zinc yellow-chromate plating significantly enhances corrosion resistance, making it ideal for outdoor or humid conditions without compromising the 150,000 psi tensile strength. Partially threaded design allows for controlled grip length, reducing stress concentration points. Commonly used in construction, automotive, and manufacturing sectors, this steel hex screw ensures reliability in heavy-duty applications where safety and durability are paramount.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit per UNF standards, ensuring dimensional accuracy and interchangeability. It conforms to ASME B18.2.1 and SAE J429 specifications for Grade 8 mechanical properties, with a tensile strength of 150,000 psi and Rockwell C33 hardness. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, guaranteeing it is free from hazardous substances and safe for industrial use worldwide.