S-91257A130 5/16"-18 x 12" 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 Grade 8 steel construction and 150,000 psi tensile strength for reliable performance in high-stress environments.
• Superior corrosion resistance provided by zinc yellow-chromate plating, extending service life in harsh or outdoor industrial settings.
• Secure and efficient installation thanks to the external hex drive and coarse UNC threading, reducing assembly time and preventing stripping.
• Optimized thread engagement with Class 2A thread fit ensuring consistent, vibration-resistant connections in machinery and structural applications.
• Enhanced durability from Rockwell C33 hardness, maintaining structural integrity under repeated loads and impacts.
• Versatile partial threading allowing for precise clamping force control in heavy-duty assemblies requiring both threaded and unthreaded sections.
• Compliance with industry standards including ASME B18.2.1 and SAE J429, guaranteeing interchangeability and reliability in professional applications.

Professional Applications & Engineering Value

This Grade 8 steel hex head screw is engineered to address critical challenges in heavy machinery, construction, and automotive industries where high tensile strength and corrosion resistance are paramount. The zinc yellow-chromate plating effectively combats rust and environmental degradation, while the coarse UNC threading and external hex drive facilitate quick, secure fastening even in high-vibration environments. Its partially threaded design allows for precise load distribution, making it ideal for bolting flanges, brackets, and structural frames that demand both durability and compliance with ASME B18.2.1 and SAE J429 specifications. This combination of material excellence and precise engineering ensures long-term reliability, reducing maintenance costs and downtime in demanding operational conditions.

Specification Summary & Compliance

This fastener adheres to Class 2A thread fit tolerances and UNC coarse thread standards, with a thread size of 5/16"-18 and a minimum thread length of 1 1/8". Manufactured in compliance with ASME B18.2.1 and SAE J429 specifications, it meets rigorous industrial requirements for dimensional accuracy and mechanical properties. The product conforms to relevant industry regulations, ensuring suitability for professional use in sectors requiring high-strength, corrosion-resistant hex head screws.