S-91211A172 3/8"-16 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

• Exceptional load-bearing capability with 150,000 PSI tensile strength and Grade 8 classification for reliable performance in high-stress environments
• Vibration-resistant locking through the nylon patch thread locker, maintaining secure fastening across temperatures from -55° to 250°F
• Superior corrosion protection with zinc yellow-chromate plating, extending service life in demanding industrial conditions
• Optimized torque transmission via the external hex drive and 9/16" head width, enabling efficient installation with standard tools
• Precision thread engagement with Class 2A fit and UNC coarse threading, ensuring consistent performance and reduced cross-threading risks
• Enhanced durability from Rockwell C33 hardness, providing excellent resistance to wear and deformation under heavy loads
• Versatile partial threading design allowing unthreaded shank sections for precise clamping in structural applications

Professional Applications & Engineering Value

Engineered for heavy-duty industrial applications, these Grade 8 hex head screws deliver critical reliability where vibration resistance and structural integrity are paramount. The nylon patch thread locking technology effectively prevents loosening in machinery, automotive assemblies, and construction equipment exposed to dynamic loads and temperature fluctuations. Manufactured from zinc yellow-chromate plated steel, these fasteners combat corrosion in harsh environments while maintaining the 150,000 PSI tensile strength required for critical connections. The 3/8"-16 UNC coarse thread configuration ensures rapid installation and superior holding power in metals and high-density materials, making them ideal for production lines requiring both speed and uncompromising safety margins.

Specification Summary & Compliance

These partially threaded hex head screws feature Class 2A thread fit tolerances and comply with ASME B18.2.1 and SAE J429 specifications for dimensional accuracy and mechanical properties. The 3 1/2" length with 1" minimum thread length provides versatile fastening solutions. Manufacturing adheres to industry standards for Grade 8 strength classification, ensuring consistent performance across industrial applications where quality assurance and regulatory compliance are essential.