S-91268A249 5/16"-18 x 5 1/2" 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, ideal for high-stress structural and machinery applications.
• Superior resistance to wear and deformation due to Grade 8 steel construction and Rockwell C33 hardness.
• Reliable fastening in coarse materials enabled by 5/16"-18 UNC coarse threading and Class 2A thread fit for consistent engagement.
• Easy installation and removal with a standard 1/2" external hex head design, compatible with common wrenches.
• Optimized for partial-thread applications where unthreaded shank provides enhanced shear strength and precise clamping.
• Long-term durability in harsh environments backed by compliance with RoHS 3 and REACH environmental regulations.
• Guaranteed interchangeability and performance through adherence to ASME B18.2.1 and SAE J429 standards.

Professional Applications & Engineering Value

This Grade 8 steel hex head screw is engineered to address critical challenges in heavy machinery, construction, and automotive assemblies where vibration and dynamic loads are common. The 5/16"-18 UNC coarse thread ensures rapid installation and robust holding power in softer or coarse-grained materials, reducing the risk of cross-threading. With a partially threaded design, the screw provides an unthreaded shank that resists shear forces, making it ideal for pinned connections or when precise clamp load is required. The external hex drive and right-hand threading facilitate straightforward torque application, while the high tensile strength and hardness prevent stripping and fatigue under repetitive stress. These features collectively enhance assembly reliability, minimize maintenance downtime, and ensure compliance with industry specifications for industrial fasteners.

Specification Summary & Compliance

This fastener features a 5/16"-18 UNC coarse thread with Class 2A thread fit for standard tolerance and easy assembly. It is manufactured from Grade 8 steel with a tensile strength of 150,000 PSI and Rockwell C33 hardness. The screw meets ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and mechanical performance. Additionally, it is RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, confirming adherence to environmental and safety standards for industrial use.