S-91771A573 1/4"-20 x 4" 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 performance under heavy loads
• Optimized drive engagement through Phillips No. 3 drive design that prevents cam-out and ensures secure installation
• Precision thread compatibility with Class 2A UNC coarse threads providing consistent fit and vibration resistance
• Flush mounting capability with standard 82° countersink angle for seamless surface integration
• Versatile partial threading allowing both secure fastening and adjustment flexibility in assembly applications
• Regulatory compliance assurance meeting ASME B18.6.3 specifications and environmental standards including RoHS 3 and REACH

Professional Applications & Engineering Value

These 1/4"-20 UNC flat head screws deliver critical engineering solutions where surface flushness and corrosion resistance are paramount. The passivated 18-8 stainless steel construction provides exceptional protection against oxidation and chemical exposure, making them ideal for marine equipment, food processing machinery, and outdoor industrial applications. The partially threaded design combines the clamping force of fully threaded sections with the clearance benefits of unthreaded shanks, preventing material distortion in precision assemblies. With 82° countersink angle and Phillips No. 3 drive, these screws ensure smooth installation and reliable performance in automated production environments where consistent drive engagement is essential for manufacturing efficiency.

Specification Summary & Compliance

Manufactured to exacting ASME B18.6.3 standards with Class 2A thread fit tolerance for consistent mating with corresponding nuts and threaded components. The UNC coarse thread profile (1/4"-20) ensures rapid assembly and superior vibration resistance. Full compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, confirming absence of restricted substances. Mechanical properties include 80,000 psi tensile strength and Rockwell B80 hardness for dependable performance in demanding industrial applications.