S-91781A103 4-40 x 1/8" ASME B18.6.3 Stainless Steel Slotted Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with 18-8 stainless steel construction and passivated finish, ensuring long-term reliability in harsh environments
• Exceptional mechanical strength delivering 80,000 psi tensile strength and Rockwell B80 hardness for demanding applications
• Precision thread engagement with Class 2A fit and UNC coarse threads providing secure fastening and vibration resistance
• Optimal flush mounting featuring an 82° countersink angle and undercut flat head design for seamless surface integration
• Full threading capability enabling maximum grip length and load distribution across the entire fastener
• Industry-standard compliance meeting ASME B18.6.3 specifications for consistent quality and interchangeability
• Environmental regulation adherence with RoHS 3 and REACH compliance for safe use in regulated industries

Professional Applications & Engineering Value

These 4-40 UNC flat head slotted screws solve critical engineering challenges where corrosion resistance, flush surface requirements, and high-strength fastening are paramount. The 18-8 stainless steel material combined with passivated finish provides exceptional protection against chemical exposure and atmospheric corrosion, making them ideal for marine equipment, food processing machinery, and outdoor industrial applications. The undercut flat head profile ensures proper seating without protrusion, while the Class 2A thread fit maintains precise tolerances for repeated assembly and disassembly. The fully threaded design maximizes holding power in thin materials and confined spaces, addressing common vibration loosening issues in precision instruments and electronic enclosures.

Specification Summary & Compliance

Manufactured to exacting ASME B18.6.3 standards with Class 2A thread fit and UNC coarse thread specifications ensuring dimensional accuracy and reliable performance. The screws feature 82° countersink angle and fully threaded construction with right-hand thread direction. Compliance certifications include RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming environmental safety and restricted substance adherence for global industrial applications.