S-91266A541 1/4"-20 x 7/8" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior vibration resistance with nylon patch thread locker that maintains secure fastening from -65° to 250°F
• Exceptional tensile strength rated at 130,000 psi for heavy-duty applications and reliable performance under stress
• Enhanced durability through black-oxide coated alloy steel construction with Rockwell C39 hardness for corrosion resistance
• Precise thread engagement with UNC Class 3A coarse threads ensuring consistent, reliable connections in industrial settings
• Optimal flush mounting with standard 82° countersink angle flat head design for seamless surface integration
• Easy installation and removal via hex drive (5/32") that prevents stripping and allows for high torque application
• Full thread coverage along the 7/8" length provides maximum grip and distribution of clamping force

Professional Applications & Engineering Value

Engineered for demanding industrial environments, these black-oxide alloy steel flat head hex screws deliver reliable performance where vibration resistance and strength are critical. The nylon patch thread locking feature prevents loosening under dynamic loads, making them ideal for machinery, automotive assemblies, and equipment subjected to thermal cycling. Their UNC Class 3A coarse threads facilitate quick assembly while maintaining precision fit, reducing installation time without compromising integrity. The 82° countersink angle ensures flush mounting in predrilled holes, preventing protrusion in confined spaces. With full threading along the 7/8" length, these screws maximize contact area for superior load distribution in metal-to-metal and structural applications.

Specification Summary & Compliance

This fastener meets ASTM F835 specifications for mechanical properties and dimensional accuracy. Threads conform to UNC Class 3A tolerances, ensuring precise fit and interchangeability. The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, containing no restricted substances. Manufacturing follows standardized parameters including right-hand thread direction, coarse thread spacing, and fully threaded design for consistent performance across industrial applications.