S-91253A321 1/4"-28 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 under high-stress conditions, reducing the risk of fastener failure in demanding applications.
• Black-oxide finish on alloy steel provides superior corrosion resistance and a durable, non-reflective surface ideal for industrial environments.
• Class 3A thread fit offers precise, tight tolerances for secure fastening and vibration resistance in machinery and equipment assemblies.
• Partial threading design allows for controlled clamp load and improved grip in materials where full threading isn't required, enhancing assembly efficiency.
• 82° countersink angle with standard flat head ensures a flush, low-profile installation, minimizing protrusion and improving safety in tight spaces.
• Hex drive (5/32") enables easy installation and removal with standard tools, reducing assembly time and labor costs.
• Compliance with ASTM F835, RoHS 3, and REACH guarantees adherence to industry standards for quality, safety, and environmental regulations.

Professional Applications & Engineering Value

These 1/4-28 UNF flat head screws are engineered to address common industrial challenges, such as vibration loosening and corrosion in harsh environments. The black-oxide alloy steel construction, combined with a Rockwell C39 hardness, provides excellent wear resistance and durability, making them ideal for heavy-duty machinery, automotive assemblies, and aerospace components. The fine UNF threads and Class 3A fit ensure precise engagement, reducing the risk of cross-threading and enhancing load distribution. With an 82° countersink angle and partial threading, they offer secure, flush mounting in metal and composite materials, streamlining installation in confined spaces while maintaining structural integrity under high tensile loads.

Specification Summary & Compliance

This product features precise Class 3A thread fit and adheres to UNF fine thread standards (1/4"-28). Manufactured in compliance with ASTM F835 specifications, it ensures consistent quality and performance. Additionally, it meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming its suitability for global industrial use without hazardous substances.