S-91257A645 3/8"-16 x 5 1/4" 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 for reliable performance in high-stress industrial applications.
• Superior corrosion resistance due to zinc yellow-chromate plating, extending service life in harsh environments.
• High hardness rating of Rockwell C33 ensures excellent wear resistance and durability under repetitive use.
• Secure fastening with precise thread fit through Class 2A UNC coarse threads, reducing the risk of cross-threading and ensuring easy installation.
• Optimized for heavy torque applications with an external hex drive and hex head design, providing superior grip and torque transmission.
• Versatile partial threading allows for both clamping and alignment functions, ideal for machinery and structural assemblies.
• Compliance with major industry standards including ASME B18.2.1 and SAE J429, ensuring consistent quality and interchangeability.

Professional Applications & Engineering Value

Engineered for demanding industrial environments, this Grade 8 hex head screw addresses critical challenges in heavy machinery, construction, and automotive assemblies. The steel material combined with zinc yellow-chromate plating provides a robust barrier against rust and chemical exposure, reducing maintenance costs and downtime. The 3/8"-16 UNC coarse thread design ensures quick assembly and reliable holding power in vibration-prone applications, while the external hex drive facilitates easy installation with standard tools. Its partially threaded configuration offers flexibility for precise joint clamping, making it a go-to solution for structural frames, equipment mounts, and other high-stress fastening needs where 150,000 PSI tensile strength is non-negotiable.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit tolerances for consistent engagement and meets ASME B18.2.1 and SAE J429 specifications for dimensional accuracy and mechanical properties. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material restrictions are upheld. The screw features a coarse UNC thread with a minimum thread length of 1 inch, manufactured to Grade 8 standards for guaranteed performance in inch-system applications.