S-90517A110 4-40 x 1/4" ASME B18.3 Tamper-Resistant Hex Drive Flat Head Screws

Key Features & Benefits at a Glance

• Enhanced tamper resistance with specialized hex drive requiring unique tools, preventing unauthorized removal in high-security environments.
• Superior corrosion resistance from 18-8 Stainless Steel and passivated finish, ensuring long-term reliability in harsh or humid conditions.
• High mechanical strength with 70,000 psi tensile strength and Rockwell B55 hardness, providing reliable load-bearing capacity for demanding applications.
• Precise thread engagement through Class 3A fit and UNC coarse threading, enabling secure fastening and vibration resistance.
• Flush mounting capability with standard 82° countersink angle and flat head design, creating a smooth surface finish and reducing snag risks.
• Full-threaded design for maximum grip along the entire 1/4" length, distributing stress evenly and improving joint integrity.
• Regulatory compliance assurance meeting ASME B18.3 standards and environmental regulations (RoHS 3, REACH), ensuring quality and safety for industrial use.

Professional Applications & Engineering Value

Engineered for industrial security and durability, this 4-40 UNC flat head tamper-resistant hex screw addresses critical challenges in access control and equipment protection. The 18-8 Stainless Steel construction with passivated finish combats corrosion in manufacturing, electronics, and outdoor installations, while the tamper-resistant hex drive deters vandalism in public infrastructure, machinery, and secure enclosures. Its Class 3A thread fit and coarse UNC threading ensure rapid assembly and resistance to loosening under vibration, making it ideal for high-stress applications where reliability is paramount. The fully threaded design enhances grip in thin materials, providing consistent performance across diverse industrial fastening scenarios.

Specification Summary & Compliance

This screw maintains precision dimensions including a 3/32" tamper-resistant drive, 0.255" head diameter, and 1/4" length with Class 3A thread fit for superior tolerance control. It adheres to ASME B18.3 manufacturing standards and features UNC coarse thread spacing for optimal performance. Compliance with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) confirms environmental safety, supporting use in regulated industries without hazardous substance concerns.