S-91781A109 4-40 x 7/16" ASME B18.6.3 Stainless Steel Slotted Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with 18-8 stainless steel construction and passivated finish, ideal for harsh industrial environments
• Superior mechanical strength offering 80,000 psi tensile strength and Rockwell B80 hardness for reliable, long-term fastening
• Precise thread engagement with Class 2A fit and UNC coarse threads ensuring secure installations and reduced cross-threading risks
• Optimal flush mounting featuring a standard flat head with 82° countersink angle for seamless surface integration
• Full threading coverage along the 7/16" length provides maximum grip and uniform stress distribution
• Broad regulatory compliance meeting ASME B18.6.3, RoHS 3, and REACH standards for safe, quality-assured usage
• Easy manual installation with slotted drive design allowing straightforward assembly using standard tools

Professional Applications & Engineering Value

These 4-40 UNC flat head slotted screws are engineered to address critical fastening challenges in precision assemblies. The 18-8 stainless steel material, enhanced by a passivated finish, provides excellent resistance to oxidation and chemical exposure, making them suitable for electronics, machinery, and outdoor equipment. The coarse UNC threads and Class 2A fit facilitate quick, accurate alignment and reduce the likelihood of stripping in soft or brittle materials. With an 82° countersink angle and flat head profile, they ensure a smooth, flush finish that prevents snagging and maintains aerodynamic or aesthetic surfaces. Ideal for applications demanding high tensile strength and regulatory adherence, these screws deliver consistent performance in automotive, aerospace, and industrial manufacturing settings.

Specification Summary & Compliance

This product adheres to ASME B18.6.3 specifications, ensuring dimensional accuracy and thread consistency. The UNC coarse threads maintain a Class 2A tolerance for reliable fit, while the fully threaded 7/16" length supports uniform load distribution. Compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) confirms the absence of hazardous substances, meeting international environmental and safety standards for industrial use.