S-90920A120 4-40 x 5/8" ASME B18.6.3 Alloy Steel Torx Flat Head Screws

Key Features & Benefits at a Glance

• Superior corrosion resistance with zinc-plated steel construction, ensuring long-term reliability in harsh industrial environments
• Enhanced torque transmission and reduced cam-out thanks to the T8 Torx drive, providing secure fastening and minimizing tool slippage
• High tensile strength of 60,000 psi and Rockwell B70 hardness for dependable performance under heavy loads and stress
• Precise Class 3A thread fit ensures tight tolerances and reliable engagement in critical assembly applications
• Full threading along the 5/8" length allows for maximum grip and uniform clamping force across the entire fastener
• Standard 82° countersink angle enables flush mounting for a clean, professional finish in countersunk holes
• Compliance with ASME B18.6.3 and environmental regulations guarantees consistent quality and safe use in regulated industries

Professional Applications & Engineering Value

These 4-40 UNC zinc-plated steel flat head screws are engineered to address common challenges in precision assembly, such as vibration loosening and corrosion-induced failure. The T8 Torx drive provides superior torque control, reducing the risk of strip-out in high-torque applications common in electronics enclosures, machinery, and automotive components. The coarse thread spacing and Class 3A thread fit ensure quick installation and reliable holding power, while the zinc plating offers a protective barrier against moisture and chemicals. Fully threaded design maximizes contact area, distributing load evenly to prevent joint failure in dynamic environments.

Specification Summary & Compliance

This fastener meets ASME B18.6.3 specifications for dimensional accuracy and performance. It features UNC coarse threads with a Class 3A thread fit for precision, and is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring environmental safety and material restrictions are adhered to.