S-91257A837 5/8"-18 x 9" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Hex Head Screws

Key Features & Benefits at a Glance

• Maximum load-bearing capacity with Grade 8 classification providing 150,000 PSI tensile strength for critical structural applications
• Superior corrosion protection through zinc yellow-chromate plating that withstands harsh industrial environments
• Precise thread engagement with UNF fine threading and Class 2A fit ensuring reliable, vibration-resistant connections
• Enhanced durability from Rockwell C33 hardness that maintains fastener integrity under extreme stress conditions
• Optimized partial threading design allowing for controlled clamping force in specific assembly requirements
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed interoperability
• Efficient installation with external hex drive and 15/16" head width providing secure tool engagement and torque application

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, this 5/8"-18 UNF Grade 8 hex head screw delivers exceptional performance in demanding environments. The steel construction with Rockwell C33 hardness ensures structural integrity under extreme loads, while the zinc yellow-chromate plating provides superior corrosion resistance in outdoor or chemically aggressive settings. The UNF fine threading offers increased tensile strength and better vibration resistance compared to coarse threads, making it ideal for machinery, construction equipment, and structural assemblies where failure is not an option. The partial threading design allows for precise unthreaded shank placement in shear-critical applications, while the 9" length accommodates thick material stacks common in industrial fabrication and heavy equipment manufacturing.

Specification Summary & Compliance

This Grade 8 hex head screw features precise Class 2A thread fit tolerances with 5/8"-18 UNF fine threading and 1 3/4" minimum thread length. Manufactured to meet ASME B18.2.1 dimensional standards and SAE J429 material specifications, ensuring consistent quality and performance. The fastener maintains 150,000 PSI tensile strength and Rockwell C33 hardness throughout, with zinc yellow-chromate plating providing corrosion protection. Compliant with industry standards for heavy-duty applications requiring reliable, high-strength fastening solutions.