S-91255A158 6-40 x 1/4" ASME B18.3 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with black-oxide coating, ideal for demanding industrial environments
• Superior holding power from fully threaded design and Class 3A fit, ensuring vibration-resistant connections
• High-strength performance with 120,000 psi tensile strength and Rockwell C39 hardness for heavy-duty applications
• Precise torque application via 5/64" hex drive, preventing stripping and enabling reliable installation
• Optimized fine thread engagement with 6-40 UNF threading, providing enhanced load distribution in thin materials
• Low-profile rounded button head design reduces snagging while maintaining aesthetic appeal
• Full regulatory compliance meeting ASME, ASTM, RoHS 3 and REACH standards for global supply chain integration

Professional Applications & Engineering Value

Engineered for precision assemblies where vibration resistance and corrosion protection are critical, these black-oxide alloy steel screws deliver exceptional performance in electronic enclosures, precision instrumentation, and aerospace components. The 6-40 UNF fine thread configuration provides superior engagement in thin-section materials while the Class 3A fit ensures minimal backlash in high-cycle applications. The fully threaded design maximizes clamping force distribution, eliminating the need for multiple fastener types in stacked assemblies. With 120,000 psi tensile strength, these rounded head screws withstand extreme mechanical stresses while the hex drive facilitates precise torque control during installation.

Specification Summary & Compliance

Manufactured to precision Class 3A thread fit with 6-40 UNF fine thread specifications. Compliant with ASME B18.3 dimensional standards and ASTM F835 mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations. Features right-hand thread direction with 0.138" thread diameter and 1/4" length.