S-90311A163 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 environments and extended service life.
• Vibration-resistant locking provided by the integrated nylon patch, preventing loosening in dynamic applications from -50° to 250°F.
• High-strength performance with 70,000 psi tensile and 35,000 psi shear strength for reliable use in demanding mechanical assemblies.
• Precise alignment and spacing ensured by the standard shoulder fit and Class 3A thread tolerance for consistent assembly quality.
• Easy installation and removal with a 5/32" hex socket drive and knurled head for improved grip and torque application.
• Broad industry compliance meeting ASME B18.3 specifications, RoHS 3, and REACH standards for safe, regulated use.
• Durable and wear-resistant design with a Rockwell B79 hardness, maintaining integrity under repetitive stress.

Professional Applications & Engineering Value

This 1/4"-20 UNC shoulder screw is engineered to address critical challenges in precision machinery, automation systems, and structural assemblies where alignment and vibration are concerns. The 316 stainless steel material offers exceptional resistance to chemicals and moisture, reducing maintenance in corrosive settings like marine or chemical processing equipment. The nylon patch thread locker secures the UNC coarse thread against shock and vibration, eliminating the need for separate locking hardware and speeding up assembly. Its socket head with knurling allows for secure tool engagement in confined spaces, while the shoulder provides accurate component positioning, making it invaluable in industrial applications requiring reliable, long-term fastening without compromise.

Specification Summary & Compliance

This shoulder screw features a Class 3A thread fit for high precision, with UNC 1/4"-20 coarse threads and a standard shoulder diameter of 5/16" (tolerance: -0.004" to -0.002") and length of 1/2" (tolerance: -0.005" to 0.005"). It is manufactured in compliance with ASME B18.3 standards and is RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) compliant, ensuring environmental safety and regulatory adherence for global industrial use.