S-91257A810 5/8"-11 x 4" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional strength for demanding applications with Grade 8 classification and 150,000 psi tensile strength, ensuring reliable performance under high stress.
• Superior corrosion resistance provided by the zinc yellow-chromate plating, extending service life in harsh industrial environments.
• Optimized for high-torque assembly thanks to the external hex drive and hex head design, allowing for secure tightening with standard tools.
• Reliable coarse threading with UNC thread type and Class 2A fit, facilitating faster installation and reducing cross-threading risks.
• Enhanced durability and wear resistance from Rockwell C33 hardness, maintaining fastener integrity over repeated use.
• Versatile partial threading offering a non-threaded shank for precise clamping in heavy 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

This Grade 8 hex head screw is engineered to address critical challenges in heavy-duty and industrial settings, where failure is not an option. The steel material combined with zinc yellow-chromate plating provides a robust barrier against corrosion, making it ideal for outdoor equipment, construction machinery, and automotive assemblies exposed to moisture and chemicals. The 5/8"-11 UNC coarse thread and partial threading design ensure secure fastening in high-vibration environments, reducing the risk of loosening. With a tensile strength of 150,000 psi and Rockwell C33 hardness, it delivers consistent performance in applications requiring high clamp loads and fatigue resistance, such as structural frames, engine components, and heavy industrial bolting. This fastener meets rigorous specifications, providing engineers and procurement specialists with a reliable solution that minimizes downtime and maintenance costs.

Specification Summary & Compliance

This hex head screw features precise Class 2A thread fit and adheres to UNC coarse thread standards with a thread size of 5/8"-11. It is manufactured in accordance with ASME B18.2.1 and SAE J429 Grade 8 specifications, ensuring dimensional accuracy and mechanical properties. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety and environmental responsibility for global supply chains.