S-91257A826 5/8"-18 x 2 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional Strength & Reliability: Grade 8 classification and 150,000 psi tensile strength ensure dependable performance in high-stress and heavy-duty applications.
• Superior Corrosion Resistance: Zinc yellow-chromate plating provides a robust protective barrier, extending service life in harsh or outdoor industrial environments.
• Precise & Secure Fastening: Fine 5/8"-18 UNF threads with a Class 2A fit offer excellent vibration resistance and reduce the risk of loosening under dynamic loads.
• Optimized for High-Torque Installation: The external hex head design allows for easy and secure engagement with standard wrenches, facilitating efficient assembly and disassembly.
• Enhanced Durability & Wear Resistance: A Rockwell C33 hardness rating ensures the screw maintains its structural integrity and resists deformation under extreme pressure.
• Versatile Partially Threaded Design: The 1 1/2" minimum thread length on a 2 1/2" long screw provides flexibility for applications requiring both clamped and unthreaded shank sections.
• Guaranteed Quality & Compliance: Manufactured to meet ASME B18.2.1 and SAE J429 standards, ensuring dimensional accuracy and material consistency for professional use.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to solve critical challenges in demanding industrial settings. Its high 150,000 psi tensile strength and Rockwell C33 hardness make it an ideal choice for heavy machinery, structural frameworks, and automotive assemblies where failure is not an option. The zinc yellow-chromate plating combats corrosion effectively, making it suitable for use in environments exposed to moisture or chemicals. The 5/8"-18 UNF fine threading provides a tighter, more secure fit compared to coarse threads, which is crucial for applications subject to vibration and dynamic stresses. The partially threaded design allows the unthreaded shank to bear shear loads directly, improving joint integrity in bolted connections. This combination of material properties and precision engineering delivers reliable, long-lasting performance in construction, manufacturing, and equipment maintenance.

Specification Summary & Compliance

This fastener adheres to strict dimensional and performance standards, including Class 2A thread fit for consistent assembly. It is manufactured in compliance with ASME B18.2.1 and SAE J429 specifications, ensuring reliability and interchangeability. The product is also confirmed to be RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting essential environmental and safety regulations for global industrial supply chains.