S-91099A167 4-40 x 1/2" 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 delivering 80,000 PSI tensile strength and Rockwell B80 hardness for reliable load-bearing performance
• Precision thread engagement with Class 2A fit and UNC coarse threading ensuring consistent, vibration-resistant fastening
• Optimized flush mounting featuring undercut flat head design with 82° countersink angle for seamless surface integration
• Enhanced drive stability through Phillips No. 1 drive system providing secure torque transmission during installation
• Full-threaded design offering maximum grip length and uniform stress distribution across the entire fastener
• Regulatory compliance assurance meeting ASME B18.6.3 specifications and environmental standards including RoHS 3 and REACH

Professional Applications & Engineering Value

These 4-40 UNC flat head screws deliver critical engineering advantages in precision assembly applications where corrosion resistance and flush surface requirements are paramount. The passivated 18-8 stainless steel construction provides exceptional protection against oxidation and chemical exposure, making them ideal for electronics enclosures, medical devices, and marine equipment. The undercut flat head profile with 82° countersink angle ensures perfect seating without protrusion, while the fully threaded right-hand design with coarse UNC threading enables rapid installation and superior holding power in both metallic and composite materials. This combination addresses common industrial challenges including vibration loosening, galvanic corrosion, and assembly efficiency in high-volume production environments.

Specification Summary & Compliance

Manufactured to exacting ASME B18.6.3 standards, these screws feature precision Class 2A thread fit with UNC coarse threads and right-hand orientation. The 1/2" length and fully threaded configuration ensure consistent performance across applications. Compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations guarantees environmental responsibility and workplace safety, while the documented 80,000 PSI tensile strength and Rockwell B80 hardness provide verified mechanical performance data for engineering specifications.