S-91257A588 5/16"-18 x 1 5/8" 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 head design, allowing for secure and efficient installation with common tools.
• Reliable thread engagement with UNC coarse threads and Class 2A fit, facilitating faster assembly and reducing cross-threading risks.
• Enhanced durability and wear resistance from Rockwell C33 hardness, maintaining fastener integrity through repeated use.
• Versatile partial threading allows for a non-threaded shank section, providing superior clamping force in specific joint designs.
• Guaranteed dimensional consistency and interchangeability by conforming to ASME B18.2.1 and SAE J429 standards.

Professional Applications & Engineering Value

This Grade 8 Hex Head Screw is engineered to solve critical challenges in heavy machinery, construction, and automotive assemblies where failure is not an option. Its 150,000 psi tensile strength and Rockwell C33 hardness directly address the need for fasteners that can withstand extreme vibrational loads and high tension without stretching or shearing. The zinc yellow-chromate plating provides a robust barrier against rust and corrosion, significantly reducing maintenance costs and downtime in corrosive environments. Featuring 5/16"-18 UNC coarse threads and an external hex drive, it ensures quick, secure installation and disassembly, making it an indispensable component for structural frames, engine components, and other industrial applications demanding exceptional strength and reliability.

Specification Summary & Compliance

This screw adheres to precise dimensional and performance criteria, including a Class 2A thread fit for consistent assembly and a minimum thread length of 7/8". It is manufactured in compliance with the ASME B18.2.1 and SAE J429 standards, ensuring quality and interchangeability. The specified inch system measurements, right-hand thread direction, and partially threaded design meet rigorous engineering specifications for industrial use.