S-91264A581 5/16"-18 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Exceptional load-bearing capacity with 140,000 psi tensile strength and 84,000 psi shear strength for reliable performance in demanding applications.
• Secure vibration-resistant locking thanks to the integrated nylon pellet thread locker, maintaining integrity across a wide temperature range from -50° to 250°F.
• Precise alignment and smooth rotation ensured by the 3/4" shoulder with tight diameter tolerance, reducing wear on mating components.
• Corrosion-resistant black oxide finish enhances durability and provides a professional appearance in harsh industrial environments.
• Easy installation and high torque capability with the hex socket drive and knurled head, preventing tool slippage during assembly.
• Interchangeable and reliable fit due to UNC coarse threading and Class 3A thread fit, ensuring compatibility with standard nuts and tapped holes.
• Long-term operational reliability supported by Rockwell C32 hardness, offering excellent resistance to deformation under stress.

Professional Applications & Engineering Value

This alloy steel shoulder screw is engineered to address critical alignment and fastening challenges in precision machinery, such as in automated assembly systems, robotic linkages, and rotating shaft applications. The 3/4" shoulder length and controlled diameter tolerance provide a stable bearing surface, minimizing misalignment and reducing friction-induced wear on moving parts. Combined with the black oxide finish, it offers enhanced corrosion resistance, extending service life in environments exposed to moisture or chemicals. The integrated nylon pellet thread locker ensures that the screw remains securely fastened even under intense vibrations, preventing loosening in dynamic operations. Its UNC coarse thread and hex socket drive facilitate quick installation and high torque application, making it ideal for maintenance-heavy industries where downtime reduction is crucial.

Specification Summary & Compliance

This shoulder screw adheres to precise dimensional standards, including Class 3A thread fit for superior accuracy and UNC thread type with 5/16"-18 size. The shoulder diameter tolerance is maintained between -0.004" to -0.002", and shoulder length tolerance from -0.005" to 0.005", ensuring consistent performance. It meets ASME B18.3 and ASTM A574 specifications for material and manufacturing quality. Additionally, it is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety and environmental standards for global industrial use.