S-91257A880 3/4"-16 x 4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 150,000 PSI ensures reliable performance in high-stress industrial applications, reducing the risk of fastener failure.
• Superior corrosion resistance with zinc yellow-chromate plating extends service life in harsh environments, minimizing maintenance and replacement costs.
• High hardness rating (Rockwell C33) provides excellent wear resistance and durability under heavy loads and vibration.
• Fine UNF threading (3/4"-16) with Class 2A fit offers precise, secure fastening and improved resistance to loosening in dynamic applications.
• External hex drive design allows for easy installation and removal with standard tools, increasing assembly efficiency.
• Partial threading provides unthreaded shank for enhanced shear strength and better clamping force distribution.
• Compliance with major standards including ASME B18.2.1 and SAE J429 ensures consistent quality and interoperability in global industrial systems.

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 steel material combined with zinc yellow-chromate plating provides a robust barrier against rust and chemical exposure, significantly extending fastener life in outdoor or corrosive environments. The 3/4"-16 UNF fine thread configuration ensures superior vibration resistance and precise tension control, making it ideal for high-stress applications such as structural connections, engine components, and industrial equipment. With partial threading, it offers optimal clamp load distribution, preventing joint failure under dynamic loads. These features collectively deliver enhanced reliability, reduced downtime, and long-term cost savings for demanding industrial applications.

Specification Summary & Compliance

This fastener maintains Class 2A thread fit for consistent assembly and meets ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance reliability. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, guaranteeing environmental safety and regulatory adherence for global supply chains.