S-91255A557 1/4"-28 x 3/4" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional corrosion resistance with black-oxide coating for prolonged service life in harsh industrial environments
• Superior thread engagement with Class 3A fit ensuring precise, vibration-resistant fastening in critical applications
• High tensile strength rating of 120,000 psi provides reliable performance under extreme mechanical stress
• Optimized drive efficiency through 5/32" hex drive design enabling secure tool engagement and reduced stripping risk
• Enhanced material durability from Rockwell C39 hardness alloy steel resisting deformation under repeated loads
• Full-threaded design maximizes grip length and distribution of clamping force across the entire fastener
• Regulatory compliance assurance meeting ASME B18.3, ASTM F835, RoHS 3 and REACH standards for global supply chain compatibility

Professional Applications & Engineering Value

These black-oxide alloy steel rounded head screws deliver critical performance advantages in precision assemblies requiring fine UNF threading and Class 3A thread fit. The combination of high-strength alloy material and protective oxide coating addresses common industrial challenges including vibrational loosening, corrosion-induced failure, and assembly inaccessibility. The rounded button head profile with hex drive configuration provides optimal clearance in confined spaces while maintaining positive drive engagement. Engineered for machinery, automotive subsystems, and electronic enclosures, these fully threaded screws ensure uniform stress distribution and reliable fastening integrity across demanding applications where 120,000 psi tensile strength and Rockwell C39 hardness are essential for long-term operational safety.

Specification Summary & Compliance

Manufactured to ASME B18.3 and ASTM F835 specifications with Class 3A thread fit precision. Features 1/4"-28 UNF fine threading with right-hand orientation and fully threaded design. Compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) environmental regulations for restricted substance control. Dimensional accuracy maintained through 0.437" head diameter and 3/4" length tolerances per applicable industrial standards.