S-91255A123 5-40 x 3/8" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with black-oxide finish, extending service life in harsh industrial environments
• Exceptional tensile strength of 120,000 psi prevents stripping and failure under heavy loads
• Precision Class 3A thread fit ensures secure fastening with minimal backlash in critical assemblies
• Full threading design provides maximum grip length and uniform stress distribution
• Hex drive compatibility with 5/64" tools enables high-torque installation without cam-out
• Coarse UNC thread profile facilitates rapid assembly and reduces cross-threading risks
• Comprehensive compliance with ASME, ASTM, RoHS 3 and REACH standards guarantees regulatory acceptance

Professional Applications & Engineering Value

These 5-40 UNC rounded head screws deliver critical performance advantages in precision machinery, automotive subsystems, and electronic enclosures where vibration resistance and dimensional stability are paramount. The black-oxide alloy steel construction provides superior protection against environmental degradation while maintaining Rockwell C39 hardness for wear resistance. The fully threaded Class 3A fit eliminates joint loosening in dynamic applications, while the hex drive configuration ensures reliable torque transmission during assembly. Engineered to meet ASME B18.3 and ASTM F835 specifications, these fasteners solve common challenges in maintenance-critical installations where disassembly frequency demands durable thread integrity.

Specification Summary & Compliance

Manufactured to exacting Class 3A thread tolerances with unified coarse (UNC) 5-40 threading and right-hand orientation. Complies with ASME B18.3 dimensional standards and ASTM F835 mechanical properties. Meets RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental compliance requirements. Features include 3/8" length, 0.238" head diameter, and 5/64" hex drive compatibility.