S-91259A589 1/4"-20 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Exceptional Tensile Strength – With 140,000 psi tensile and 84,000 psi shear strength, this screw withstands high-stress applications without failure, ensuring reliable performance in demanding environments.
• Superior Corrosion Resistance – The black oxide finish provides a durable protective layer, reducing wear and extending service life in humid or corrosive industrial settings.
• Precision Thread Fit – Class 3A UNC coarse threads offer tight, secure fastening with reduced risk of cross-threading, enhancing assembly efficiency and joint integrity.
• Knurled Head for Enhanced Grip – The knurled socket head design allows for easy manual handling and tool engagement, minimizing slippage during installation and maintenance.
• High Hardness for Durability – Rockwell C32 hardness ensures the screw maintains its shape and thread integrity under repeated loads, ideal for machinery and automotive uses.
• Accurate Shoulder Dimensions – Tight tolerances on shoulder diameter and length (-0.004" to -0.002" and -0.005" to 0.005" respectively) guarantee consistent alignment and smooth rotational movement in pivoting applications.
• Compliant with Industry Standards – Meets ASME B18.3 specifications and is RoHS 3 and REACH compliant, ensuring safety, environmental responsibility, and global acceptance.

Professional Applications & Engineering Value

This alloy steel shoulder screw is engineered to address common industrial challenges such as misalignment, vibration loosening, and corrosion in high-load assemblies. Its 1/4"-20 UNC coarse thread and Class 3A fit provide secure fastening with excellent resistance to dynamic stresses, making it ideal for precision machinery, automotive linkages, and robotic arms. The black oxide finish not only enhances corrosion resistance but also reduces friction, prolonging the life of moving parts. With a robust 1 3/4" shoulder length and precise tolerances, it ensures accurate positioning and smooth rotation in bushings or bearings, minimizing wear and maintenance downtime in industrial automation and equipment manufacturing.

Specification Summary & Compliance

This shoulder screw adheres to Class 3A thread fit and UNC coarse thread standards, with dimensional tolerances including shoulder diameter (-0.004" to -0.002") and length (-0.005" to 0.005"). It is manufactured in compliance with ASME B18.3 and ASTM A574 specifications, and meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations, ensuring high performance and regulatory acceptance in global markets.