S-90298A204 4-40 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel construction and passivated finish, ensuring longevity in harsh industrial environments.
• Exceptional thread precision with Class 3A UNC threads for reliable, vibration-resistant fastening in high-stress assemblies.
• Accurate shoulder positioning thanks to tight diameter tolerance (±0.001") and controlled shoulder length, enabling precise component alignment.
• High tensile strength of 70,000 psi and Rockwell B55 hardness for dependable performance under heavy mechanical loads.
• Easy installation and removal with a standard hex socket drive (5/64"), allowing secure tool engagement in confined spaces.
• Broad regulatory compliance including ASME B18.3, RoHS 3, and REACH, ensuring safety and environmental standards are met.
• Versatile coarse threading (UNC) for quick assembly and disassembly, reducing maintenance time in production settings.

Professional Applications & Engineering Value

This 4-40 UNC Class 3A stainless steel shoulder screw is engineered to address critical alignment and durability challenges in precision mechanical systems. The 18-8 stainless steel material combined with a passivated finish provides excellent resistance to corrosion and wear, making it ideal for applications in automotive, aerospace, and industrial machinery where exposure to moisture or chemicals is common. The 1/8" shoulder diameter with minimal tolerance ensures exact positioning of components like gears, pulleys, or bearings, reducing misalignment and extending equipment life. Its high tensile strength and coarse UNC threads offer secure fastening in high-vibration environments, while the hex socket drive simplifies installation in tight spaces. This screw delivers reliable performance in assemblies requiring repeatable accuracy and long-term reliability.

Specification Summary & Compliance

This shoulder screw adheres to Class 3A thread fit for precise UNC threading, with a shoulder diameter tolerance of -0.001" to 0.001" and shoulder length tolerance of -0.005" to 0.005" to ensure consistent quality. It meets ASME B18.3 specifications for dimensional standards and is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, guaranteeing environmental safety and material integrity.