S-90550A210 4-40 x 1/4" ASME B18.3, ASTM F879, MIL-DTL-18240 Venting Stainless Steel Hex-Drive Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel construction, ideal for harsh environments and long-term reliability.
• Precise thread engagement with Class 3A fit and UNC coarse threads, ensuring secure fastening and vibration resistance.
• Efficient installation and removal via the 1/16" hex drive, providing excellent torque transfer and reducing tool slippage.
• Flush surface finish with an 82° countersink angle and standard flat head profile, enabling seamless integration into assemblies.
• Enhanced pressure equalization through the vented feature, preventing pressure buildup in sensitive applications.
• Full threading along the 1/4" length for maximum grip and load distribution across the entire fastener.
• Compliance with major industrial standards including ASME B18.3, ensuring consistent quality and interchangeability.

Professional Applications & Engineering Value

These 4-40 UNC flat head screws are engineered to address critical challenges in precision assemblies, such as electronics, aerospace components, and medical devices. The 18-8 stainless steel material offers excellent resistance to oxidation and chemical exposure, reducing maintenance needs in corrosive settings. The Class 3A thread fit and coarse UNC threading provide reliable, high-strength connections that resist loosening under dynamic loads. The vented design and 82° countersink angle allow for secure, flush mounting while facilitating air or fluid flow in enclosed systems. This combination of hex drive efficiency and fully threaded construction ensures quick installation and robust performance, making them ideal for applications demanding tight tolerances and durability.

Specification Summary & Compliance

This product adheres to Class 3A thread fit for precise dimensional accuracy and utilizes UNC coarse threads (4-40 size) with right-hand direction. Manufacturing and quality are governed by ASME B18.3, ASTM F879, and MIL-DTL-18240 specifications. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material restrictions are met.