S-91381A671 4-40 x 1/4" ASME B18.3 Set Screws

Key Features & Benefits at a Glance

• Superior vibration resistance with brass soft tip that prevents damage to mating surfaces while maintaining secure positioning
• Exceptional durability provided by black-oxide alloy steel construction with Rockwell C28 hardness for long service life
• Precise thread engagement through Class 3A thread fit ensuring reliable fastening in demanding applications
• Easy installation and removal with 0.050" hex drive design that accommodates standard tools
• Optimized for industrial environments with corrosion-resistant black-oxide coating and regulatory compliance
• Secure fastening performance through UNC coarse thread spacing that resists loosening under vibration
• Space-saving design with headless configuration ideal for confined spaces and flush mounting requirements

Professional Applications & Engineering Value

This 4-40 UNC set screw delivers exceptional engineering value in applications requiring precise component positioning and vibration resistance. The black-oxide alloy steel construction combined with Rockwell C28 hardness provides optimal strength-to-weight ratio, making it ideal for machinery, automotive assemblies, and precision equipment where reliable fastening is critical. The brass soft tip eliminates marring of shaft surfaces while maintaining positive contact, particularly valuable in adjustable mechanisms and rotating assemblies. The headless design with hex drive allows for flush installation in confined spaces, while the Class 3A thread fit ensures consistent performance in high-vibration environments. This combination of features addresses common industrial challenges of component slippage, surface damage, and maintenance accessibility.

Specification Summary & Compliance

This precision fastener features 4-40 UNC coarse threads with Class 3A thread fit for superior dimensional accuracy and engagement. Manufactured to ASME B18.3 specifications, the set screw maintains strict tolerance control throughout production. The product is fully RoHS 3 (2015/863/EU) compliant and meets REACH (EC 1907/2006) requirements, ensuring environmental responsibility and regulatory adherence for global industrial applications. The combination of material specifications, thread standards, and compliance certifications guarantees consistent performance and reliability across diverse operating conditions.