S-91255A121 5-40 x 1/4" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional Durability: With 120,000 psi tensile strength and Rockwell C39 hardness, these screws withstand high-stress applications without stripping or breaking.
• Superior Corrosion Resistance: Black-oxide coating on alloy steel provides reliable protection against rust and environmental degradation in harsh industrial settings.
• Precision Thread Fit: Class 3A UNC coarse threads ensure tighter tolerances and secure fastening with reduced risk of cross-threading or loosening under vibration.
• Optimized Torque Transmission: Hex drive (5/64") design allows for efficient installation with standard tools, minimizing slippage and enhancing assembly speed.
• Versatile Industrial Compatibility: Rounded button head profile distributes clamping force evenly while maintaining a low-profile appearance for machinery and equipment.
• Regulatory Compliance Assurance: Meets ASME B18.3 and ASTM F835 specifications, plus RoHS 3 and REACH environmental standards for global supply chain integration.
• Full Thread Engagement: Fully threaded 1/4" length provides maximum grip strength across the entire fastener for consistent load distribution.

Professional Applications & Engineering Value

Engineered for demanding industrial environments, these Black-Oxide Alloy Steel Rounded Head Screws solve critical fastening challenges where vibration resistance and corrosion protection are paramount. The 5-40 UNC coarse threading with Class 3A fit prevents loosening in dynamic equipment while the hex drive ensures reliable torque application during high-volume assembly. Ideal for machinery manufacturing, automotive subsystems, and electronic enclosures, the combination of 120,000 psi tensile strength and Rockwell C39 hardness provides lasting performance in applications requiring repeated disassembly. The black-oxide surface treatment extends service life in humid or chemically exposed conditions without compromising dimensional stability.

Specification Summary & Compliance

Manufactured to Class 3A thread fit tolerances per UNC standards with 5-40 coarse thread configuration. Complies with ASME B18.3 dimensional specifications and ASTM F835 mechanical properties. Fully certified for RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations. Alloy steel composition ensures consistent performance across temperature variations while maintaining 1/4" length and 0.238" head diameter precision.