S-98070A138 4-40 x 5/16" Sealing Stainless Steel Phillips Flat Head Screws

Key Features & Benefits at a Glance

• Superior Sealing Performance with Buna-N rubber O-ring rated for up to 1500 psi pressure and temperatures from -40° to 225°F, ensuring reliable leak prevention in demanding environments.
• Excellent Corrosion Resistance thanks to 18-8 stainless steel construction and passivated finish, ideal for harsh industrial and outdoor applications.
• Precise Thread Engagement with UNC coarse threads and Class 2A fit, providing consistent, vibration-resistant fastening in various materials.
• Flush Mounting Capability featuring an undercut flat head design that sits seamlessly in countersunk holes, reducing protrusion and improving aesthetics.
• Effortless Installation with Phillips No. 1 drive, allowing for quick, secure tightening using standard tools without stripping.
• Durable Material Strength offering 70,000 psi tensile strength, ensuring long-term reliability under mechanical stress.
• Environmental Compliance meeting RoHS 3 and REACH standards, making them safe for regulated industries and global supply chains.

Professional Applications & Engineering Value

Engineered for high-pressure sealing in industrial equipment, these 4-40 UNC flat head screws with Buna-N O-rings solve critical leakage issues in hydraulic systems, pneumatic controls, and fluid handling assemblies. The 18-8 stainless steel and passivated finish resist corrosion from moisture, chemicals, and extreme temperatures, extending service life in marine, automotive, and manufacturing settings. The undercut flat head ensures a secure, flush fit, while the coarse UNC threads and Class 2A fit provide quick, stable installation in metals and plastics, reducing assembly time and maintenance costs. Ideal for OEMs and MRO professionals needing reliable, compliant fasteners for sealed enclosures and pressure vessels.

Specification Summary & Compliance

This screw features a 4-40 UNC coarse thread with Class 2A tolerance for precise fit, fully threaded for maximum grip. Dimensions include a 5/16" length, 0.224" head diameter, and 100° countersink angle. Manufactured from 18-8 stainless steel with passivated finish, it complies with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and suitability for global industrial use.