S-91771A116 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, ensuring long-term reliability in harsh industrial environments.
• High tensile strength of 80,000 psi provides exceptional load-bearing capacity and resistance to mechanical failure in demanding applications.
• Rockwell B80 hardness offers excellent durability and wear resistance, maintaining fastener integrity through repeated use.
• Class 2A thread fit with UNC coarse threading ensures easy, quick installation and secure fastening in various materials.
• 82° countersink angle and flat head design allows for a flush, professional finish that minimizes protrusion and snagging risks.
• Phillips No. 1 drive enables efficient, tool-compatible driving with reduced cam-out for faster assembly cycles.
• Full threading along the 1-1/8" length maximizes grip and adjustment flexibility across the entire fastener.

Professional Applications & Engineering Value

These 4-40 UNC flat head screws are precision-engineered from passivated 18-8 stainless steel to address common industrial challenges like corrosion, vibration loosening, and assembly inefficiency. The coarse UNC thread and Class 2A fit provide reliable engagement in metals, plastics, and composites, reducing cross-threading risks during high-volume production. The 82° countersink angle ensures a seamless fit in pre-drilled holes, ideal for applications requiring aerodynamic or aesthetic surfaces, such as enclosures, machinery panels, and electronic housings. With a Phillips No. 1 drive, these screws support rapid installation with standard tools, enhancing workflow speed while maintaining 80,000 psi tensile strength for structural integrity in automotive, aerospace, and OEM equipment.

Specification Summary & Compliance

This product adheres to ASME B18.6.3 specifications for dimensional accuracy and performance, featuring a Class 2A thread fit per UNC standards for consistent interchangeability. The fully threaded 1-1/8" length and right-hand thread direction comply with industrial norms, while material and manufacturing processes meet RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring safe, sustainable use in global supply chains.