S-91870A290 5/16"-18 x 1 1/4" ASME B18.3 Tamper-Resistant Torx Stainless Steel Flat Head Screws

Key Features & Benefits at a Glance

• Superior tamper resistance with specialized T40 Torx drive design prevents unauthorized removal in high-security applications
• Exceptional corrosion resistance through 18-8 stainless steel construction and passivated finish for long-term reliability in harsh environments
• High mechanical strength with 70,000 psi tensile strength and Rockwell B70 hardness withstands heavy loads and vibration
• Optimized flush installation with standard 82° countersink angle and flat head profile for smooth surface finishing
• Reliable thread engagement through UNC coarse threading and Class 2A fit ensures secure fastening in various materials
• Full-thread coverage across the entire 1-1/4" length provides maximum holding power and adjustment flexibility
• Regulatory compliance meets ASME B18.3 standards and environmental regulations for global industrial use

Professional Applications & Engineering Value

This 18-8 stainless steel flat head screw with tamper-resistant T40 Torx drive addresses critical security and durability challenges in industrial applications. The combination of passivated finish and stainless steel material provides exceptional resistance to corrosion, moisture, and chemical exposure, making it ideal for outdoor equipment, marine applications, and harsh manufacturing environments. The UNC coarse thread with Class 2A fit ensures reliable installation in various substrates while the 82° countersink angle creates a flush surface that eliminates protrusions in machinery, electronic enclosures, and public infrastructure. The fully threaded design maximizes grip length and distributes stress evenly, preventing loosening under vibration and thermal cycling. These security screws are particularly valuable for applications requiring permanent or tamper-proof fastening in access panels, utility boxes, and industrial machinery where unauthorized access must be prevented.

Specification Summary & Compliance

This heavy-duty fastener features precision 5/16"-18 UNC coarse threads with Class 2A dimensional tolerance for consistent performance. Manufacturing and dimensional specifications strictly comply with ASME B18.3 standards, ensuring interchangeability and reliability. The product meets RoHS 3 (2015/863/EU) compliance for hazardous substance restriction and REACH (EC 1907/2006) regulations for chemical safety. Mechanical properties include 70,000 psi tensile strength and Rockwell B70 hardness, validated through quality control processes. The passivated surface treatment enhances corrosion resistance while maintaining the material's inherent properties.