S-91771A894 4-40 x 1 1/8" ASME B18.6.3 Stainless Steel Phillips Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with passivated 18-8 stainless steel construction for extended service life in harsh environments
• Exceptional mechanical strength with 80,000 PSI tensile strength and Rockwell B80 hardness for reliable load-bearing performance
• Precision thread engagement with Class 2A fit and UNC coarse threads ensuring secure fastening and vibration resistance
• Flush mounting capability featuring undercut flat head design with 82° countersink angle for seamless surface integration
• Optimized drive efficiency with No. 1 Phillips drive providing positive torque transmission and reduced cam-out risk
• Full-length threading offering maximum grip range and versatility across various material thicknesses
• Regulatory compliance meeting ASME B18.6.3 manufacturing standards and environmental regulations for global industrial use

Professional Applications & Engineering Value

These 4-40 UNC flat head Phillips screws deliver critical engineering solutions where surface flushness and corrosion resistance are paramount. The passivated 18-8 stainless steel construction provides excellent protection against oxidation and chemical exposure, making them ideal for electronics enclosures, precision instruments, and marine components. The undercut flat head profile ensures complete seating without protrusion, while the coarse UNC threading maintains secure fastening in vibration-prone applications. With full threading along the 1 1/8" length, these screws accommodate varying material depths while the 82° countersink angle matches standard chamfer preparations. The combination of 80,000 PSI tensile strength and Rockwell B80 hardness ensures reliable performance in high-stress assemblies without compromising installation efficiency.

Specification Summary & Compliance

Manufactured to ASME B18.6.3 specifications with Class 2A thread fit tolerances ensuring precise dimensional accuracy. Features 4-40 UNC coarse threads with right-hand direction and complete threading along the 1 1/8" length. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming adherence to international substance restriction standards for industrial components.