S-93310A578 5/16"-18 x 1/2" ASME B18.3, ASTM F879, MIL-DTL-18240 Thread-Locking Stainless Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Vibration-resistant locking with permanent nylon patch ensures secure fastening in high-stress environments, preventing loosening under dynamic loads.
• Superior corrosion resistance from 18-8 stainless steel construction maintains integrity and appearance in harsh or humid conditions.
• High tensile strength of 70,000 psi provides reliable load-bearing capacity for demanding industrial applications.
• Wide temperature tolerance (-70° to 250°F) allows consistent performance across extreme thermal cycles without degradation.
• Precise Class 3A thread fit with UNC coarse threading ensures easy installation and secure engagement in tapped holes.
• Hex drive (3/16") design facilitates efficient installation with standard tools, reducing assembly time and effort.
• Rounded button head profile offers a low-profile, aesthetically clean finish while minimizing snagging risks.

Professional Applications & Engineering Value

Engineered for critical assemblies where vibration resistance and material durability are paramount, these 18-8 stainless steel rounded head screws integrate a permanent nylon patch lock to eliminate the need for secondary locking devices. The UNC coarse threads with Class 3A fit provide superior engagement in metals and plastics, reducing cross-threading risks during high-volume production. Ideal for machinery, automotive subsystems, and outdoor enclosures, the fully threaded design ensures uniform clamp load distribution. Combined with temperature resilience and high tensile strength, they address common failure points in dynamic or thermally fluctuating environments, extending service life and reducing maintenance intervals.

Specification Summary & Compliance

This screw features a 5/16"-18 UNC coarse thread with Class 3A precision fit, ensuring dimensional accuracy per ASME B18.3. Manufactured to MIL-DTL-18240 and ASTM F879 specifications, it guarantees consistent performance in defense and industrial applications. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) standards, it is free from restricted substances, supporting global supply chain requirements.