S-91253A112 4-40 x 5/8" 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.
• Precise Class 3A thread fit provides superior engagement and vibration resistance, minimizing loosening in machinery and equipment.
• Black-oxide coating on alloy steel offers enhanced corrosion resistance and a durable, non-reflective finish suitable for industrial environments.
• Fully threaded design with coarse UNC spacing allows for faster installation and maximum grip length in various materials.
• 82° countersink angle and flat head profile enable a flush, secure fit that prevents snagging and improves aesthetic integration.
• Hex drive (1/16") facilitates easy installation and removal with standard tools, reducing assembly time and labor costs.
• High Rockwell C39 hardness ensures long-term durability and resistance to wear, extending the screw's service life.

Professional Applications & Engineering Value

These 4-40 UNC flat head screws are engineered to address common industrial challenges such as vibration-induced loosening and material fatigue. The Black-Oxide Alloy Steel construction, combined with a Class 3A thread fit, ensures secure fastening in precision assemblies like electronic enclosures, machinery frames, and automotive components. The fully threaded coarse spacing provides excellent holding power in softer materials, while the 82° countersink angle allows for a seamless finish that meets stringent design specifications. Ideal for applications requiring high tensile strength and compliance with industry standards, these screws deliver consistent performance in manufacturing, aerospace, and equipment maintenance sectors.

Specification Summary & Compliance

This product adheres to Class 3A thread tolerance for precise fit and UNC coarse thread standards. It meets ASME B18.3 and ASTM F835 specifications for dimensional accuracy and performance. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material restrictions are upheld.