S-91257A855 3/4"-10 x 5" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – With a 150,000 psi tensile strength and Rockwell C33 hardness, this screw withstands extreme loads and high-stress conditions, minimizing the risk of failure in critical applications.
• Superior Corrosion Resistance – The zinc yellow-chromate plating provides a durable barrier against rust and environmental degradation, extending service life in harsh industrial or outdoor settings.
• Reliable Thread Engagement – The UNC coarse thread and Class 2A thread fit ensure easy, secure installation and consistent clamping force, reducing assembly time and improving joint integrity.
• Optimized for Heavy-Duty Use – The partially threaded design concentrates strength where needed, preventing thread damage and offering superior performance in structural and machinery applications.
• High-Strength Material Compliance – Manufactured from Grade 8 steel, this screw meets rigorous standards for high-strength fasteners, ensuring dependable performance under demanding conditions.
• Secure External Hex Drive – The external hex head and 1 1/8" width allow for high torque application with standard tools, providing a firm grip and reducing slippage during installation.
• Industry Standard Conformity – Compliant with ASME B18.2.1, RoHS 3, and REACH, this screw meets essential safety and environmental regulations for global industrial use.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to address common challenges in heavy machinery, construction, and automotive assemblies where vibration, high loads, and corrosive environments are prevalent. The 3/4"-10 UNC coarse thread and Class 2A thread fit deliver precise, reliable fastening that resists loosening under dynamic stresses. The zinc yellow-chromate plating significantly enhances corrosion resistance, making it ideal for outdoor equipment or humid conditions. With a partially threaded shank, the screw provides unthreaded grip length for better shear strength and alignment in structural connections, reducing the risk of thread stripping. Its 150,000 psi tensile strength and Rockwell C33 hardness ensure it performs reliably in critical applications such as bolting large flanges, heavy-duty frames, and industrial machinery, where failure is not an option.

Specification Summary & Compliance

This fastener adheres to precise dimensional and performance criteria, including a Class 2A thread fit for consistent assembly and UNC coarse threading per inch-system standards. It meets the ASME B18.2.1 specification for hex bolts and is manufactured in compliance with SAE J429 Grade 8 requirements. Additionally, it conforms to RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances and suitable for use in regulated markets.