S-91253A721 1/2"-13 x 2 1/4" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 130,000 psi ensures reliable performance in heavy-duty applications, reducing the risk of fastener failure.
• Superior corrosion resistance from the black-oxide finish extends service life in harsh industrial environments, minimizing maintenance needs.
• Precision Class 3A thread fit provides tighter tolerances for secure, vibration-resistant connections in critical assemblies.
• Fully threaded design offers consistent holding power along the entire length, enhancing load distribution and joint integrity.
• 82° countersink angle allows for a flush, professional finish when installed, improving aesthetics and safety in visible applications.
• Hex drive compatibility with 5/16" drive enables quick, high-torque installation using standard tools, boosting assembly efficiency.
• Compliance with ASME B18.3 and ASTM F835 guarantees consistent quality and interchangeability, streamlining procurement and inventory management.

Professional Applications & Engineering Value

These black-oxide alloy steel flat head screws are engineered to address common industrial challenges such as vibration loosening, corrosion, and high-stress fatigue. The UNC coarse thread spacing and Class 3A thread fit ensure rapid installation and superior resistance to dynamic loads in machinery, structural steel frameworks, and heavy equipment. The fully threaded right-hand design maximizes grip in thick materials, while the 82° countersink angle provides a secure, flush fit that prevents snagging and maintains aerodynamic or aesthetic surfaces. Ideal for industrial assembly, construction, and automotive applications, these screws deliver long-term reliability under demanding conditions, reducing downtime and replacement costs.

Specification Summary & Compliance

This product features precise Class 3A thread fit per UNC standards, with a thread size of 1/2"-13 and coarse spacing for optimal engagement. Manufacturing adheres to ASME B18.3 and ASTM F835 specifications, ensuring dimensional accuracy and performance consistency. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, supporting environmentally responsible sourcing and use in global markets.