S-91266A535 1/4"-20 x 3/8" ASTM F835 Alloy Steel Thread-Locking Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Vibration-resistant locking: Nylon patch thread locker provides reliable fastening that stays secure even under continuous vibration and shock loads.
• Exceptional strength for demanding applications: Made from alloy steel with a tensile strength of 130,000 psi, ensuring high load-bearing capacity and resistance to shear forces.
• Superior corrosion protection: Black-oxide coating enhances durability and provides a protective barrier against rust and corrosion in harsh environments.
• Precise and reliable thread engagement: UNC coarse threads with Class 3A fit guarantee consistent, high-quality connections and easier assembly.
• Wide temperature tolerance: Performs reliably in temperatures from -65° to 250° F, making it suitable for both extreme cold and high-heat applications.
• Flush, professional finish: Standard flat head with an 82° countersink angle allows for a smooth, seated installation that minimizes protrusion and snagging.
• Secure hex drive installation: 5/32" hex drive enables high-torque tightening with standard tools, reducing the risk of stripping and ensuring a firm hold.

Professional Applications & Engineering Value

This black-oxide alloy steel flat head hex screw is engineered to solve critical industrial challenges, such as component loosening due to vibration and thermal cycling. The nylon patch thread locking technology embedded in the UNC coarse threads creates a permanent, chemical-free bond that maintains clamp load without the need for additional lock washers or adhesives. Its fully threaded design and Class 3A thread fit ensure maximum engagement in tapped holes, providing uniform stress distribution and reducing the risk of thread failure. Ideal for machinery, automotive assemblies, and electronic enclosures, this screw delivers long-term reliability in environments where temperature fluctuations and dynamic loads are common, preventing downtime and maintenance costs.

Specification Summary & Compliance

This screw features a 1/4"-20 UNC coarse thread with a precision Class 3A thread fit for consistent assembly. It is manufactured in compliance with ASTM F835 specifications, ensuring dimensional accuracy and performance reliability. The product is also RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, meeting stringent environmental and safety standards for use in global markets.