S-91781A107 4-40 x 5/16" ASME B18.6.3 Stainless Steel Slotted Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel construction and passivated finish for extended service life in harsh environments
• Exceptional mechanical strength with 80,000 psi tensile strength and Rockwell B80 hardness for reliable performance under heavy loads
• Precision thread engagement with Class 2A fit and UNC coarse threads ensuring secure fastening and vibration resistance
• Optimized flush mounting featuring standard 82° countersink angle for seamless surface integration and reduced protrusion
• Full-threaded design providing maximum grip length and uniform stress distribution across the entire fastener
• Industry-standard compliance meeting ASME B18.6.3 specifications for dimensional accuracy and performance reliability
• Environmental responsibility with RoHS 3 and REACH compliance for safe use in regulated applications

Professional Applications & Engineering Value

These 4-40 UNC flat head slotted screws deliver critical performance advantages in precision assembly applications where surface flushness and corrosion resistance are paramount. The combination of 18-8 stainless steel material and passivated finish creates a robust barrier against chemical exposure and atmospheric corrosion, significantly extending service intervals in industrial equipment, electronic enclosures, and marine components. The fully threaded design with Class 2A thread fit ensures consistent clamping force distribution, while the standardized 82° countersink angle provides reliable seating in precision-machined surfaces. These flat head fasteners are engineered to solve common challenges of vibration loosening, material degradation, and installation efficiency in demanding industrial applications.

Specification Summary & Compliance

Manufactured to exacting ASME B18.6.3 standards with Class 2A thread tolerances for precision fit and reliable performance. The UNC coarse thread profile (4-40) with right-hand direction ensures compatibility with standard components. Full regulatory compliance includes RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) requirements, confirming environmental safety and material restrictions adherence. Dimensional specifications include 5/16" length, 0.212" head diameter, and standardized flat head profile for consistent installation across industrial fastener systems.