S-91253A128 5-40 x 1/2" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with black-oxide coating for extended service life in demanding industrial environments
• Superior thread engagement with Class 3A fit ensuring precise, vibration-resistant fastening in critical applications
• High-strength performance delivering 130,000 psi tensile strength for reliable load-bearing capabilities
• Optimized flush mounting with standard 82° countersink angle for seamless surface integration
• Enhanced torque transmission through hex drive design preventing cam-out during installation
• Full threading coverage providing maximum grip length and uniform stress distribution
• Regulatory compliance assurance meeting ASME B18.3, ASTM F835, RoHS 3 and REACH standards

Professional Applications & Engineering Value

These 5-40 UNC flat head screws with black-oxide alloy steel construction address critical engineering challenges in industrial fastening systems. The Class 3A thread fit ensures superior vibration resistance in machinery and equipment subjected to dynamic loads, while the coarse thread spacing facilitates quicker assembly in production environments. The hex drive design provides positive torque transmission, eliminating stripping issues common in high-torque applications. The 82° countersink angle creates flush surface mounting ideal for aerospace components, electronic enclosures, and precision instruments where protrusion-free profiles are essential. With Rockwell C39 hardness, these screws maintain structural integrity under repeated stress cycles, making them suitable for automotive assemblies, industrial machinery, and heavy equipment manufacturing where reliability cannot be compromised.

Specification Summary & Compliance

Manufactured to precise inch system dimensions with Class 3A thread fit tolerance for superior engagement. Thread specifications conform to UNC coarse thread standard with right-hand orientation. Compliant with ASME B18.3 dimensional requirements and ASTM F835 mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe use in global industrial markets. Fully threaded design maintains consistent 5-40 UNC thread form throughout the 1/2" length for uniform load distribution.