S-92210A355 4-40 x 1/8" ASME B18.3, ASTM F879, MIL-DTL-18240 Stainless Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel material, ideal for harsh industrial environments and extended service life.
• Exceptional thread reliability with Class 3A fit, ensuring precise engagement and reducing the risk of cross-threading or loosening.
• High mechanical strength offering 70,000 psi tensile strength and Rockwell B55 hardness for dependable performance under load.
• Optimized flush mounting via the undercut flat head and 82° countersink angle, providing a secure, low-profile finish.
• Efficient installation and removal with the hex drive style, allowing for high torque application and reduced tool slippage.
• Versatile coarse thread (UNC) design for quicker assembly and better performance in softer materials or where debris is present.
• Full threading along the 1/8" length maximizes grip and load distribution across the entire fastener.

Professional Applications & Engineering Value

This 4-40 UNC flat head screw is engineered to address critical assembly challenges in precision industries such as aerospace, electronics, and machinery. The 18-8 stainless steel construction provides excellent resistance to oxidation and chemical exposure, making it suitable for outdoor or corrosive settings. The Class 3A thread fit ensures tight tolerances, minimizing backlash and enhancing joint integrity in vibration-prone applications. With its undercut head profile and 82° countersink angle, it achieves a seamless flush finish, preventing protrusion and improving aerodynamic or aesthetic surfaces. The hex drive facilitates secure tool engagement, speeding up installation in confined spaces while the coarse thread spacing offers rapid assembly and reliable holding power in various substrates.

Specification Summary & Compliance

This screw adheres to precise dimensional standards with a Class 3A thread fit per UNC specifications, ensuring high accuracy and interchangeability. It is manufactured in compliance with ASME B18.3, ASTM F879, and MIL-DTL-18240 standards, guaranteeing consistent quality and performance. Additionally, it meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its environmental and safety compliance for global use.