S-91099A450 1/4"-20 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, ideal for harsh industrial environments
• Exceptional mechanical strength with 80,000 psi tensile strength and Rockwell B80 hardness for heavy-duty applications
• Precise flush mounting through undercut flat head design with 82° countersink angle for seamless surface integration
• Reliable driving performance with No. 3 Phillips drive that resists cam-out during high-torque installation
• Optimized thread engagement with Class 2A thread fit and coarse UNC threading for secure fastening in various materials
• Full-thread coverage along the 1/2" length ensures maximum grip strength and vibration resistance
• Regulatory compliance assurance meeting ASME B18.6.3 standards and environmental regulations including RoHS 3 and REACH

Professional Applications & Engineering Value

These 1/4"-20 UNC flat head Phillips screws deliver critical engineering advantages in demanding applications where corrosion resistance and structural integrity are paramount. The passivated 18-8 stainless steel construction provides exceptional protection against chemical exposure and atmospheric corrosion, making these industrial flat head screws ideal for marine equipment, food processing machinery, and outdoor structural assemblies. The undercut flat head profile with 82° countersink angle ensures flush mounting without protrusion, preventing snagging hazards while maintaining aerodynamic or hydraulic flow characteristics. The combination of coarse UNC threading and Class 2A thread fit provides reliable fastening in both metallic and composite materials, while the fully threaded design distributes clamping force evenly across the entire engagement length. These heavy-duty fasteners solve common industrial challenges including vibration-induced loosening, galvanic corrosion, and installation efficiency in high-volume production environments.

Specification Summary & Compliance

Manufactured to exacting dimensional standards with Class 2A thread fit tolerance for consistent performance across applications. The 1/4"-20 UNC coarse thread specification ensures compatibility with standard industrial components. These screws conform to ASME B18.6.3 mechanical and dimensional requirements, guaranteeing interchangeability and reliability. Environmental compliance includes RoHS 3 (2015/863/EU) restrictions on hazardous substances and REACH (EC 1907/2006) regulations for chemical safety. The 82° countersink angle and flat head undercut design meet industry-standard chamfer specifications for proper seating in countersunk holes.