S-91253A104 4-40 x 3/16" ASTM F835 Alloy Steel Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Exceptional durability with Rockwell C39 hardness and 130,000 psi tensile strength for reliable performance in demanding applications
• Superior corrosion resistance thanks to the black-oxide finish on alloy steel, extending service life in harsh environments
• Precise thread engagement with Class 3A fit and UNC coarse threads ensuring secure fastening and vibration resistance
• Optimal flush mounting featuring an 82° countersink angle and standard flat head profile for seamless surface integration
• Easy installation and removal with hex drive design providing superior torque transmission and tool accessibility
• Full thread coverage across the entire 3/16" length for maximum grip strength and load distribution
• Regulatory compliance assurance meeting ASME B18.3 and ASTM F835 standards while being RoHS 3 and REACH compliant

Professional Applications & Engineering Value

These 4-40 UNC flat head screws deliver critical engineering solutions where space constraints and surface finish matter. The black-oxide alloy steel construction provides exceptional corrosion resistance while maintaining 130,000 psi tensile strength, making them ideal for aerospace, electronics, and precision machinery applications. The Class 3A thread fit ensures tight tolerances for vibration-resistant assemblies, while the 82° countersink angle allows for perfect flush mounting in tapered recesses. The hex drive design enables high-torque installation without cam-out issues, and the fully threaded configuration maximizes holding power in thin materials. These industrial screws solve common challenges of fastener failure, corrosion, and installation efficiency in critical precision fastening applications.

Specification Summary & Compliance

Manufactured to exacting Class 3A thread fit tolerances with UNC coarse thread spacing and right-hand threading. These flat head screws feature precise dimensional control with 0.255" head diameter and 3/16" length. Compliance includes ASME B18.3 and ASTM F835 specifications, ensuring consistent quality and performance. Environmental compliance is verified with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) adherence, making them suitable for global industrial applications requiring regulated materials management.