S-91257A416 1/4"-20 x 9" 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 for reliable performance in high-stress applications
• Superior corrosion resistance through zinc yellow-chromate plating that protects against harsh industrial environments
• Optimized thread engagement with UNC coarse threading and Class 2A fit ensuring secure fastening and vibration resistance
• Enhanced durability from Rockwell C33 hardness providing excellent wear resistance and long service life
• Easy installation and removal with external hex drive design allowing for standard wrench access and high torque application
• Partial threading design offering both gripping strength in threaded sections and shear resistance in unthreaded portions
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed quality and interchangeability

Professional Applications & Engineering Value

This Grade 8 hex head screw delivers critical engineering solutions for heavy machinery, structural assemblies, and industrial equipment where failure is not an option. The zinc yellow-chromate plated steel construction provides exceptional corrosion protection in demanding environments, while the 1/4"-20 UNC coarse thread with Class 2A fit ensures reliable fastening even under vibration and dynamic loads. The partially threaded design combines the benefits of maximum clamping force in the threaded section with enhanced shear strength in the unthreaded shank. Engineered to ASME B18.2.1 standards, these heavy-duty hex screws offer predictable performance and dimensional consistency across industrial applications including construction equipment, automotive assemblies, and manufacturing machinery.

Specification Summary & Compliance

This fastener maintains precise Class 2A thread fit tolerances according to ASME standards, ensuring proper engagement and interchangeability. The 1/4"-20 UNC coarse thread configuration follows established industrial threading specifications, while the 9" length with 1" minimum thread length provides consistent dimensional accuracy. Manufacturing complies with ASME B18.2.1 and SAE J429 specifications, guaranteeing material quality, mechanical properties, and dimensional conformity. The zinc yellow-chromate plating meets industry standards for corrosion protection while maintaining compliance with relevant environmental regulations for industrial applications.