S-90311A168 1/4"-20 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 316 stainless steel construction, ideal for harsh industrial and marine environments.
• Reliable vibration resistance provided by the integrated nylon patch thread locker, maintaining secure fastening from -50° to 250° F.
• High strength and durability with a tensile strength of 70,000 psi and shear strength of 35,000 psi, ensuring long-term performance under heavy loads.
• Precise alignment and smooth rotation due to the 1-3/4" shoulder length and standard shoulder fit, reducing wear in moving assemblies.
• Easy installation and removal with a hex drive (5/32") and knurled head, offering a secure grip and efficient tool engagement.
• Accurate thread engagement with Class 3A thread fit and coarse UNC threading, providing consistent and reliable connections.
• Compliance with industry standards including ASME B18.3, RoHS 3, and REACH, ensuring safety and environmental responsibility.

Professional Applications & Engineering Value

This 1/4"-20 UNC shoulder screw is engineered to address common industrial challenges such as misalignment, vibration loosening, and corrosion. Made from 316 stainless steel, it offers excellent resistance to chemicals and moisture, making it suitable for applications in machinery, automotive, and marine equipment. The nylon patch locking feature secures the fastener against vibrations, which is critical in dynamic systems like conveyor belts or rotating shafts. The coarse thread and precise Class 3A thread fit ensure quick assembly and reliable performance, while the extended shoulder provides stable bearing surfaces for pivots or spacers, reducing maintenance needs and downtime in precision engineering setups.

Specification Summary & Compliance

This shoulder screw features a Class 3A thread fit with UNC threading for precise dimensional accuracy. It meets ASME B18.3 manufacturing standards and is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances. The shoulder diameter tolerance is -0.004" to -0.002", and shoulder length tolerance is -0.005" to 0.005", guaranteeing consistent performance in industrial applications.