S-91211A127 1/4"-20 x 2 1/2" ASME B18.2.1, SAE J429 High-Strength Grade 8 Steel Thread-Locking Hex Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant secure locking with permanent nylon patch thread locker that maintains integrity across extreme temperature ranges from -55°F to 250°F
• Exceptional load-bearing capacity with Grade 8 classification delivering 150,000 psi tensile strength for heavy-duty applications
• Superior corrosion protection through zinc yellow-chromate plating that extends service life in demanding industrial environments
• Optimized torque transmission via external hex drive design that prevents tool slippage and ensures proper installation
• Reliable thread engagement with Class 2A fit UNC coarse threads that provide consistent fastening performance
• Enhanced durability with Rockwell C33 hardness that resists wear and deformation under high stress conditions
• Versatile partial threading that allows for precise clamping force distribution across connected components

Professional Applications & Engineering Value

These Grade 8 hex head screws with nylon patch thread locker address critical vibration-induced loosening challenges in industrial machinery, automotive assemblies, and structural applications. The zinc yellow-chromate plated steel construction provides exceptional corrosion resistance while maintaining mechanical properties in harsh environments. The UNC coarse thread design ensures rapid installation and reliable performance in materials where fine threads might be problematic. With 150,000 psi tensile strength and temperature stability from -55° to 250°F, these partially threaded fasteners deliver consistent clamping force while preventing rotation-induced failures in high-vibration settings common in manufacturing equipment, transportation systems, and heavy machinery applications.

Specification Summary & Compliance

Manufactured to precise Class 2A thread fit tolerances with UNC coarse threading (1/4"-20) and partial threading configuration. Complies with ASME B18.2.1 specifications and SAE J429 standards for Grade 8 fasteners. Meets REACH compliance requirements (EC 1907/2006) and maintains dimensional accuracy per industrial fastener specifications. The external hex drive design ensures compatibility with standard industrial tools while the specified thread locker temperature range guarantees performance across operational extremes.