S-90311A171 5/16"-18 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Vibration-resistant locking: Permanent nylon patch thread locker ensures secure fastening, preventing loosening in high-vibration environments.
• Superior corrosion resistance: Made from 316 Stainless Steel for excellent performance in harsh or corrosive conditions.
• High-strength reliability: 70,000 psi tensile strength and 35,000 psi shear strength provide dependable performance in demanding applications.
• Precision thread fit: Class 3A UNC coarse threads offer a tighter, more precise fit for improved assembly accuracy and load distribution.
• Wide temperature tolerance: Thread locker remains effective from -50° to 250°F, ensuring stability across diverse operating environments.
• Secure, non-slip handling: Knurled socket head provides enhanced grip for easier installation and removal with standard hex tools.
• Dimensional consistency: Tight shoulder diameter and length tolerances ensure reliable alignment and fit in assembled components.

Professional Applications & Engineering Value

This 5/16"-18 UNC shoulder screw is engineered to solve critical fastening challenges in precision assemblies. The 316 Stainless Steel construction provides exceptional resistance to corrosion, making it ideal for marine, chemical processing, and food industry applications where moisture and chemicals are present. The integrated nylon patch thread locker eliminates the need for separate locking washers or adhesives, providing a permanent, vibration-resistant lock that maintains integrity from -50° to 250°F. The Class 3A thread fit ensures precise engagement with mating components, reducing play and improving load distribution across the 1/2" shoulder length. These features make it particularly valuable in machinery, automation systems, and precision instruments where secure positioning and reliable alignment are critical to operational safety and performance.

Specification Summary & Compliance

This shoulder screw features Class 3A thread fit with UNC coarse threads (5/16"-18) and precise shoulder dimensions (3/8" diameter with -0.004" to -0.002" tolerance, 1/2" length with -0.005" to 0.005" tolerance). Manufactured to ASME B18.3 specifications and compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations. The fastener meets rigorous quality standards with Rockwell B79 hardness and is suitable for applications requiring high tensile strength (70,000 psi) and reliable performance in demanding industrial environments.