S-91211A193 1/2"-13 x 3 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Thread-Locking Hex Head Screws

Key Features & Benefits at a Glance

• Permanent vibration resistance with integrated nylon patch thread locker, eliminating the need for separate locking washers and preventing loosening under extreme conditions
• Exceptional load-bearing capacity with Grade 8 strength rating and 150,000 psi tensile strength, ensuring reliable performance in heavy-duty applications
• Superior corrosion protection through zinc yellow-chromate plating, providing durable defense against rust and environmental degradation
• Wide temperature tolerance from -55° to 250°F, maintaining locking performance and structural integrity across diverse operating environments
• Optimized installation efficiency with external hex drive and coarse UNC threads, enabling quick assembly with standard tools while reducing cross-threading risks
• Precision thread fit with Class 2A tolerance, ensuring smooth engagement and consistent clamping force in demanding applications
• Enhanced durability with Rockwell C33 hardness, providing excellent wear resistance and long service life under repetitive stress

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications where vibration resistance and structural integrity are critical, these Grade 8 hex head screws solve common fastening failures in machinery, construction equipment, and automotive assemblies. The nylon patch thread locking technology creates permanent friction that prevents back-off under continuous vibration, eliminating downtime from loose connections. The zinc yellow-chromate plated steel construction provides superior corrosion protection in harsh environments, while the partially threaded UNC coarse thread design ensures optimal clamping force distribution. With 150,000 psi tensile strength and Rockwell C33 hardness, these screws maintain performance in high-stress applications where standard fasteners would fail, making them ideal for structural connections, heavy machinery, and critical infrastructure projects requiring reliable, long-term fastening solutions.

Specification Summary & Compliance

This 1/2"-13 x 3 1/2" hex head screw features Class 2A thread fit tolerance for precise engagement and UNC coarse threading for efficient installation. Manufactured to meet ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance consistency. The fastener complies with industry standards for Grade 8 strength classification with verified 150,000 psi tensile strength and Rockwell C33 hardness. The nylon patch thread locker maintains effectiveness across the specified temperature range of -55° to 250°F, providing reliable performance in various environmental conditions while meeting quality assurance requirements for industrial fastening applications.