S-90298A203 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 long-term reliability in harsh environments.
• Exceptional mechanical strength offering 70,000 psi tensile strength and Rockwell B55 hardness for high-stress applications.
• Precision alignment and spacing via a 1/8" shoulder diameter with a tight ±0.001" tolerance, minimizing assembly misalignment.
• Secure and reliable fastening with Class 3A thread fit and UNC coarse threads, providing excellent vibration resistance.
• Easy installation and removal using a standard 5/64" hex socket drive, reducing tooling time and effort.
• Broad regulatory compliance including ASME B18.3, RoHS 3, and REACH, ensuring safety and environmental standards are met.
• Consistent dimensional accuracy with controlled shoulder length (±0.005") and thread specifications for repeatable performance.

Professional Applications & Engineering Value

This 4-40 UNC thread shoulder screw is engineered to address critical alignment and durability challenges in precision assemblies. The 18-8 Stainless Steel material, combined with a passivated finish, provides excellent resistance to corrosion and oxidation, making it ideal for use in electronics, machinery, and automotive components exposed to moisture or chemicals. The socket head design with a hex drive allows for compact installation in confined spaces, while the Class 3A thread fit ensures tight, secure connections that resist loosening under vibration. Its shoulder feature acts as a precise spacer or pivot point, reducing wear and maintaining part alignment in rotating or sliding mechanisms. By integrating high tensile strength and strict dimensional tolerances, this screw enhances assembly longevity and reduces maintenance needs in demanding industrial settings.

Specification Summary & Compliance

This shoulder screw adheres to ASME B18.3 specifications, with a Class 3A thread fit for superior engagement and UNC coarse threads ensuring quick assembly. Dimensional precision is maintained with a shoulder diameter tolerance of -0.001" to 0.001" and shoulder length tolerance of -0.005" to 0.005". The product is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming it is free from hazardous substances and safe for various industrial applications.