S-91771A574 1/4"-20 x 4 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 with 80,000 psi tensile strength and Rockwell B80 hardness for reliable performance under heavy loads
• Precise thread engagement with Class 2A thread fit ensuring consistent assembly and vibration resistance
• Optimized drive efficiency with Phillips No. 3 drive style providing secure torque transmission and reduced cam-out risk
• Versatile partial threading design allowing for both secure fastening and adjustable positioning in assemblies
• Industry-standard compliance meeting ASME B18.6.3 specifications for dimensional accuracy and interchangeability
• Environmental responsibility with RoHS 3 and REACH compliance for safe use in regulated industries

Professional Applications & Engineering Value

These 1/4"-20 UNC flat head screws deliver critical engineering solutions where flush mounting and high-strength fastening are paramount. The passivated 18-8 stainless steel construction provides exceptional resistance to corrosion and chemical exposure, making them ideal for marine, food processing, and outdoor industrial equipment applications. The 82° countersink angle and standard flat head profile ensure seamless surface integration while the coarse UNC threading enables rapid installation in various materials. With partial threading and Class 2A thread fit, these screws maintain precise clamping force while preventing cross-threading issues in high-vibration environments. The combination of 80,000 psi tensile strength and Rockwell B80 hardness ensures reliable performance in structural assemblies and machinery where mechanical stress is a constant concern.

Specification Summary & Compliance

This 4 1/2" flat head screw features precise 1/4"-20 UNC coarse threading with Class 2A thread fit tolerance for consistent engagement. Manufacturing complies with ASME B18.6.3 standards for dimensional accuracy and mechanical properties. The product meets RoHS 3 (2015/863/EU) compliance for hazardous substance restrictions and REACH (EC 1907/2006) regulations for chemical safety. Threading is partially applied with minimum 1 1/2" thread length, and the 82° countersink angle conforms to industry standards for flush mounting applications.