S-91255A128 5-40 x 5/8" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with black-oxide coating for extended service life in demanding environments
• Exceptional mechanical strength with 120,000 psi tensile strength and Rockwell C39 hardness for heavy-duty applications
• Precise Class 3A thread fit ensures secure, vibration-resistant connections in critical assemblies
• Optimized hex drive design (5/64") provides reliable torque transmission and reduces tool slippage
• Fully threaded construction delivers maximum engagement and load distribution along the entire fastener length
• Rounded button head profile offers low-profile installation with improved aesthetic appearance
• Comprehensive compliance with major industrial standards for quality assurance and regulatory acceptance

Professional Applications & Engineering Value

These 5-40 UNC Class 3A Rounded Head Screws deliver exceptional engineering value in industrial applications where vibration resistance and corrosion protection are critical. The black-oxide alloy steel construction provides superior durability against environmental factors, while the coarse UNC threading ensures rapid installation and reliable performance in high-stress assemblies. The combination of 120,000 psi tensile strength and Rockwell C39 hardness makes these fully threaded screws ideal for machinery, equipment manufacturing, and automotive applications where precision fastening and long-term reliability are essential. The 5/64" hex drive design facilitates efficient installation in confined spaces, reducing assembly time while maintaining industrial-grade performance.

Specification Summary & Compliance

These Rounded Head Screws feature precision Class 3A thread fit with 5-40 UNC coarse threading and are manufactured to exacting dimensional standards. The fasteners comply with ASME B18.3 and ASTM F835 specifications, ensuring consistent quality and performance. Environmental compliance includes RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) requirements, making them suitable for global industrial applications. The 5/8" length and fully threaded design provide versatile fastening solutions while maintaining strict dimensional accuracy throughout production.