S-91259A403 4-40 ASME B18.3, ASTM A574 Shoulder Screws

Key Features & Benefits at a Glance

• Exceptional strength and durability with alloy steel construction and Rockwell C32 hardness, ensuring reliable performance in high-stress applications
• Precise shoulder fit and alignment thanks to the 1/8" shoulder diameter with tight tolerances, reducing assembly errors and improving component stability
• High load-bearing capacity with 140,000 psi tensile strength and 84,000 psi minimum shear strength, ideal for heavy-duty industrial use
• Corrosion-resistant black oxide finish provides enhanced protection against rust and wear, extending service life in harsh environments
• Easy installation and removal with standard hex socket drive and coarse 4-40 UNC threads, speeding up assembly while maintaining secure fastening
• Compliance with industry standards including ASME B18.3, RoHS 3, and REACH, ensuring safety, quality, and environmental responsibility
• Right-hand thread direction and Class 3A fit for consistent, vibration-resistant connections in machinery and precision equipment

Professional Applications & Engineering Value

This alloy steel shoulder screw is engineered to address critical challenges in precision assembly and machinery, where misalignment and component failure can lead to costly downtime. The 1/8" shoulder diameter with controlled tolerances ensures accurate positioning of parts like bearings, gears, and pulleys, reducing wear and improving operational efficiency. The black oxide finish adds a layer of corrosion resistance, making it suitable for environments exposed to moisture or chemicals. With its 4-40 UNC coarse thread and Class 3A fit, it provides secure fastening in applications requiring high shear and tensile strength, such as automotive systems, aerospace components, and industrial robots. The hex socket drive allows for easy torque application in confined spaces, streamlining maintenance and reducing installation time.

Specification Summary & Compliance

This shoulder screw features precise dimensions, including a shoulder diameter of 1/8" with tolerance from -0.004" to -0.002" and length of 3/4" with tolerance -0.005" to 0.005". Thread specifications include 4-40 UNC coarse thread with Class 3A fit for tight, reliable engagement. It meets ASME B18.3 manufacturing standards and is compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances and suitable for global industrial use.