S-91263A139 5-40 x 3/8" 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 under high-stress conditions, reducing the risk of fastener failure in demanding applications.
• Superior corrosion resistance provided by the zinc-plated alloy steel construction, extending service life and maintaining integrity in harsh industrial environments.
• Precise Class 3A thread fit guarantees tight, secure fastening with minimal play, enhancing assembly accuracy and vibration resistance.
• Fully threaded design with UNC coarse threads enables quick installation and maximum grip along the entire length, improving holding power.
• Standard 82° countersink angle allows for a flush, low-profile finish that minimizes protrusion and prevents snagging in assembled components.
• Hex drive compatibility (5/64") facilitates easy installation and removal with standard tools, speeding up maintenance and reducing labor time.
• Compliance with major industry standards including ASME B18.3 and ASTM F835 ensures consistent quality and interoperability in regulated applications.

Professional Applications & Engineering Value

These 5-40 UNC flat head screws are engineered to address critical challenges in industrial assembly, where vibration resistance, corrosion protection, and high tensile strength are paramount. The zinc-plated alloy steel material provides excellent durability against environmental factors, while the Class 3A thread fit and coarse UNC threading ensure secure, reliable fastening even in high-vibration machinery and equipment. The fully threaded design and 82° countersink angle allow for seamless integration into metal, plastic, and composite assemblies, making them ideal for automotive, aerospace, and heavy machinery applications where flush mounting and maximum load distribution are required. By combining robust material properties with precise manufacturing, these screws reduce maintenance frequency and enhance long-term operational reliability.

Specification Summary & Compliance

This product features a 5-40 UNC coarse thread with Class 3A thread fit for high precision and tight tolerances. It is manufactured in accordance with ASME B18.3 and ASTM F835 specifications, ensuring dimensional accuracy and performance consistency. The screw is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its suitability for use in environmentally sensitive and regulated industries without hazardous substances.