S-91771A108 4-40 x 3/8" 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, ideal for harsh environments and extended service life.
• High tensile strength of 80,000 PSI ensures reliable fastening under significant mechanical stress and vibration.
• Class 2A thread fit with UNC coarse threading provides easy assembly and secure holding power in a wide range of materials.
• 82° countersink angle and flat head design allows for a flush, professional finish, reducing snagging and improving safety.
• Fully threaded shank maximizes grip length and load distribution for stronger, more uniform clamping force.
• Phillips drive (No. 1 size) offers common tool compatibility and efficient installation with reduced cam-out risk.
• Compliance with ASME B18.6.3, RoHS 3, and REACH guarantees consistent quality, safety, and environmental responsibility.

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 such as corrosion, high stress, and assembly efficiency. The fully threaded design and coarse UNC thread ensure quick, secure fastening in metals, plastics, and composites, reducing installation time and minimizing loosening in vibrating equipment. With an 82° countersink angle, they sit flush in pre-drilled holes, providing a smooth surface that prevents interference in machinery, electronics enclosures, and automotive components. The Phillips drive allows for widespread tool use, enhancing workflow in maintenance, manufacturing, and OEM applications where reliability and compliance with ASME B18.6.3 standards are critical.

Specification Summary & Compliance

This screw adheres to precise dimensional tolerances, including a Class 2A thread fit for consistent engagement and a length of 3/8". It meets ASME B18.6.3 specifications for mechanical and dimensional requirements, ensuring interoperability and performance. The product is fully RoHS 3 (2015/863/EU) Compliant and REACH (EC 1907/2006) Compliant, confirming it is free of hazardous substances and suitable for global industrial and electronic applications.