S-91211A151 5/16"-18 x 3" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Thread-Locking Hex Head Screws

Key Features & Benefits at a Glance

• Exceptional strength and durability with Grade 8 classification and 150,000 psi tensile strength for reliable performance in demanding applications
• Secure vibration-resistant locking through nylon patch thread locker that maintains integrity across a wide temperature range (-55° to 250°F)
• Superior corrosion protection provided by zinc yellow-chromate plating on steel construction for extended service life
• Precise thread engagement with Class 2A thread fit and UNC coarse threading for easier assembly and consistent performance
• Optimized drive efficiency through external hex head design allowing for high torque application and secure installation
• Versatile partial threading enabling both clamping force and clearance where needed in assembly configurations
• Industry-standard compliance meeting ASME B18.2.1 and SAE J429 specifications for guaranteed quality and interoperability

Professional Applications & Engineering Value

These Grade 8 hex head screws deliver critical performance advantages in heavy machinery, construction equipment, and automotive assemblies where vibration resistance and structural integrity are paramount. The nylon patch locking feature effectively prevents loosening under dynamic loads, while the zinc yellow-chromate plated steel construction provides essential corrosion protection in challenging environments. The UNC coarse thread design ensures rapid installation and reliable engagement in various materials, and the external hex drive accommodates standard tools for efficient maintenance. With 150,000 psi tensile strength and Rockwell C33 hardness, these fasteners maintain clamping force under extreme conditions, making them ideal for structural connections, equipment frames, and high-stress industrial applications requiring dependable, long-term fastening solutions.

Specification Summary & Compliance

This fastener features Class 2A thread fit tolerance for consistent engagement, UNC coarse threading (5/16"-18), and partial threading with minimum 7/8" thread length. Manufacturing complies with ASME B18.2.1 and SAE J429 specifications, ensuring dimensional accuracy and performance reliability. The construction meets industry standards for heavy-duty fasteners with verified material properties and surface treatment specifications.