S-91327A284 4-40 ASME B18.3 Shoulder Screws

Key Features & Benefits at a Glance

• Vibration-resistant locking with permanent nylon patch thread locker that maintains integrity from -50° to 250°F, preventing loosening in dynamic applications
• Superior corrosion resistance thanks to 18-8 stainless steel construction and passivated finish, ensuring longevity in harsh environments
• High-strength performance with 70,000 psi tensile strength and Rockwell B55 hardness for reliable load-bearing in demanding assemblies
• Precision alignment enabled by the 1/2" shoulder with tight diameter tolerance, providing accurate component positioning
• Secure fastening through Class 3A thread fit and UNC coarse threading, offering excellent engagement and resistance to stripping
• Easy installation with standard hex socket drive (5/64"), allowing efficient torque application in confined spaces
• Regulatory compliance with ASME B18.3 standards, RoHS 3, and REACH, ensuring safety and environmental responsibility

Professional Applications & Engineering Value

This 4-40 UNC shoulder screw delivers exceptional engineering value in precision assemblies where component alignment and vibration resistance are critical. The 18-8 stainless steel material combined with passivated finish provides reliable corrosion protection for industrial equipment exposed to moisture, chemicals, or outdoor elements. The integrated nylon patch thread locker eliminates the need for separate locking hardware, maintaining clamp force in high-vibration environments such as robotics, automotive systems, and machinery. The 1/2" shoulder length with controlled tolerances ensures precise spacing and rotational alignment of gears, bearings, and linkages, while the socket head design facilitates installation in tight spaces. With 70,000 psi tensile strength, this heavy-duty fastener withstands substantial mechanical loads without compromising joint integrity.

Specification Summary & Compliance

This shoulder screw features Class 3A thread fit for precise engagement with UNC 4-40 coarse threading. The shoulder maintains diameter tolerance of -0.004" to -0.002" and length tolerance of -0.005" to 0.005" for consistent performance. Manufacturing complies with ASME B18.3 specifications for dimensional accuracy and quality. The product is fully RoHS 3 (2015/863/EU) compliant and REACH (EC 1907/2006) compliant, meeting current environmental regulations for hazardous substance restrictions.