S-91257A979 1"-8 x 8 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 and Grade 8 classification, ensuring reliable performance in high-stress applications.
• Superior corrosion resistance from zinc yellow-chromate plating, extending service life in harsh industrial environments.
• High durability and wear resistance due to Rockwell C33 hardness, minimizing deformation under heavy loads.
• Secure and precise fastening with Class 2A thread fit and coarse UNC threading, reducing cross-threading risks and enabling quick installation.
• Optimized for high-torque applications featuring an external hex drive and 1 1/2" head width, allowing for easy wrench access and tight fastening.
• Versatile partial threading design providing strong grip on materials while allowing unthreaded shank sections to bear shear forces effectively.
• Compliance with 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 delivers critical engineering solutions for heavy machinery, structural steel connections, and industrial equipment assembly. The 1"-8 UNC coarse thread design ensures rapid installation and reliable holding power in thick materials, while the partial threading configuration provides enhanced resistance to vibrational loosening. The zinc yellow-chromate plating offers superior protection against rust and chemical exposure in demanding environments such as construction, automotive, and manufacturing facilities. With its 150,000 psi tensile strength and Rockwell C33 hardness, this fastener maintains structural integrity under extreme mechanical stress, preventing joint failure and reducing maintenance downtime. The external hex drive design accommodates standard tools for efficient installation in confined spaces.

Specification Summary & Compliance

This 8 1/2" length hex head screw features precise Class 2A thread fit tolerances and 1"-8 UNC coarse threading manufactured to ASME B18.2.1 and SAE J429 specifications. The fastener is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use across various industrial sectors. The combination of steel material, zinc yellow-chromate finish, and Grade 8 strength classification provides a reliable solution for critical fastening applications requiring dimensional accuracy and long-term performance.