S-91781A108 4-40 x 3/8" 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 delivering 80,000 psi tensile strength and Rockwell B80 hardness for reliable, vibration-resistant fastening
• Precision thread engagement with Class 2A fit and UNC coarse threads ensuring smooth installation and consistent clamping force
• Optimized flush mounting featuring standard 82° countersink angle for seamless surface integration and reduced snagging risks
• Full-threaded design providing maximum grip length and load distribution across the entire fastener length
• Industry-standard compliance meeting ASME B18.6.3 specifications for dimensional accuracy and performance reliability
• Environmental regulation adherence with RoHS 3 and REACH compliance for safe use in regulated industries

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 provides exceptional protection against oxidation and chemical exposure, making them ideal for electronic enclosures, instrumentation, marine components, and food processing equipment. The fully threaded design ensures maximum thread engagement in shallow mounting scenarios, while the standard 82° countersink angle facilitates perfect flush mounting in precision-machined components. With coarse thread spacing and Class 2A thread fit, these screws resist loosening under vibration while maintaining consistent clamping force in demanding industrial environments.

Specification Summary & Compliance

This flat head slotted screw features precise dimensional characteristics including 4-40 UNC thread size, 3/8" length, and Class 2A thread fit per ASME B18.6.3 specifications. The manufacturing process ensures consistent thread diameter of 0.112" with right-hand thread direction and coarse thread spacing. Regulatory compliance includes full adherence to ASME B18.6.3 dimensional standards, RoHS 3 (2015/863/EU) restrictions on hazardous substances, and REACH (EC 1907/2006) chemical safety requirements for industrial applications.