S-91257A636 3/8"-16 x 3" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – With 150,000 psi tensile strength and Grade 8 classification, this screw provides reliable performance in high-stress applications, reducing the risk of fastener failure.
• Superior Corrosion Resistance – The zinc yellow-chromate plating offers enhanced protection against rust and environmental degradation, extending service life in harsh conditions.
• Optimized Thread Design – Coarse UNC threading ensures quick assembly and secure fastening, even in materials where fine threads might strip or fail.
• High Hardness & Durability – Rockwell C33 hardness provides excellent wear resistance, maintaining thread integrity and drive features through repeated use.
• Precision Thread Fit – Class 2A thread fit guarantees consistent engagement and ease of installation, minimizing cross-threading and improving assembly efficiency.
• Partially Threaded Shank – Allows for unthreaded grip length, providing better clamping force and vibration resistance in structural and machinery applications.
• Regulatory Compliance – Meets ASME B18.2.1 and SAE J429 standards, and is RoHS 3 & REACH compliant, ensuring safe and approved use across regulated industries.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered for demanding environments where reliability is non-negotiable. The steel construction combined with zinc yellow-chromate plating delivers superior corrosion resistance, making it ideal for outdoor machinery, construction equipment, and automotive assemblies exposed to moisture and chemicals. The UNC coarse threading and Class 2A thread fit ensure rapid installation and secure holding power, reducing assembly time while preventing loosening under vibration. With a partially threaded design, it provides enhanced clamping in bolted joints, distributing stress effectively and minimizing fatigue failure. These screws are trusted in heavy-duty applications such as structural framing, industrial machinery, and transportation systems, where high tensile strength and durability are critical to operational safety and longevity.

Specification Summary & Compliance

This fastener adheres to ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance reliability. The thread fit is Class 2A, providing standard manufacturing tolerances for consistent engagement. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming the absence of restricted hazardous substances. The screw features a 3/8"-16 UNC coarse thread, 3" length, and external hex drive for straightforward installation using common tools.