S-91255A039 5/16"-18 x 4" ASTM F835 Steel Button Head Hex-Drive Screws

Key Features & Benefits at a Glance

• Exceptional tensile strength of 120,000 psi ensures reliable performance under heavy loads and prevents fastener failure in demanding applications
• Superior corrosion resistance from black-oxide coating extends service life and maintains integrity in harsh industrial environments
• Precision Class 3A thread fit provides tighter tolerances for secure fastening with reduced risk of loosening in vibration-prone equipment
• Heavy-duty alloy steel construction with Rockwell C39 hardness offers excellent durability and resistance to wear and deformation
• Convenient 3/16" hex drive allows for quick installation and removal with standard tools, reducing assembly time and labor costs
• Fully threaded UNC coarse spacing enables deeper penetration and faster installation while maintaining strong holding power
• Comprehensive regulatory compliance including RoHS 3 and REACH ensures environmental safety and meets international manufacturing standards

Professional Applications & Engineering Value

These black-oxide alloy steel rounded head screws deliver critical engineering solutions where vibration resistance, corrosion protection, and high tensile strength are paramount. The Class 3A UNC thread specification provides superior thread engagement compared to standard fasteners, making them ideal for precision machinery, heavy equipment assemblies, and structural applications where loosening under dynamic loads poses significant operational risks. The combination of 120,000 psi tensile strength and Rockwell C39 hardness ensures these hex drive screws maintain clamping force in high-stress environments while the black-oxide surface treatment provides essential protection against oxidation in industrial settings. Their fully threaded coarse spacing design allows for rapid installation in production environments while maintaining exceptional pull-out resistance, making them particularly valuable for assembly lines requiring both speed and reliability.

Specification Summary & Compliance

Manufactured to exacting Class 3A thread fit tolerances with UNC coarse thread specifications (5/16"-18). Complies with ASME B18.3 and ASTM F835 manufacturing standards for dimensional accuracy and mechanical properties. Meets environmental regulations including RoHS 3 (2015/863/EU) compliance and REACH (EC 1907/2006) requirements for hazardous substance restrictions. Features right-hand thread direction with standard rounded button head profile and fully threaded shank configuration.