S-91257A839 5/8"-11 x 4 3/4" 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 the fastener's service life in harsh industrial environments.
• Optimized for quick and secure assembly featuring a coarse UNC thread and external hex drive for efficient installation with common tools.
• Enhanced durability and wear resistance from the Rockwell C33 hardness, maintaining thread integrity through repeated use.
• Precise and reliable thread engagement with a Class 2A thread fit, reducing the risk of cross-threading and ensuring consistent clamping force.
• Versatile partial threading design allows for unthreaded shank sections to bear shear loads effectively, ideal for a range of structural connections.
• Compliance with major industry standards including ASME B18.2.1 and SAE J429, guaranteeing quality and interchangeability for professional use.

Professional Applications & Engineering Value

This Grade 8 hex head screw is engineered to solve critical fastening challenges in heavy machinery, construction, and automotive assemblies where high tensile strength and corrosion resistance are paramount. The zinc yellow-chromate plating provides a robust barrier against oxidation, significantly reducing maintenance needs in exposed or humid conditions. Its UNC coarse threading and external hex drive facilitate rapid installation and removal, even in high-vibration environments, minimizing downtime. The partially threaded design ensures that the unthreaded portion can carry shear loads, making it an ideal choice for bolted joints in structural steel, equipment frames, and other industrial applications demanding both strength and precision.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit tolerances for consistent assembly and is manufactured in accordance with ASME B18.2.1 and SAE J429 specifications. It meets the dimensional and mechanical property requirements for Grade 8 fasteners, ensuring reliability in high-stress applications. The product is RoHS and REACH compliant, supporting use in regulated industries.