S-91900A911 4-40 x 5/16" ASME B18.3 Tamper-Resistant Torx Stainless Steel Button Head Screws

Key Features & Benefits at a Glance

• Enhanced tamper resistance with T8 Torx drive, preventing unauthorized access in secure applications
• Superior corrosion protection from 18-8 stainless steel construction and passivated finish, ideal for harsh environments
• High mechanical strength with 70,000 psi tensile strength and Rockwell B70 hardness for reliable, long-term performance
• Precise thread engagement with Class 3A fit and UNC coarse threading, ensuring secure fastening and reduced cross-threading risk
• Full-threaded design providing maximum grip and load distribution across the entire 5/16" length
• Rounded button head profile offering a low-profile, aesthetically clean finish while minimizing snagging
• Compliance with major standards including ASME B18.3, RoHS 3, and REACH, ensuring quality and environmental responsibility

Professional Applications & Engineering Value

This 4-40 UNC thread rounded head screw is engineered to address critical industrial challenges where security, durability, and precision are paramount. The 18-8 stainless steel material, combined with a passivated finish, provides exceptional resistance to oxidation and chemical exposure, making it suitable for electronics, medical devices, and outdoor equipment. The tamper-resistant T8 Torx drive ensures that fasteners remain securely in place in public or high-security settings, reducing maintenance and vandalism risks. With a Class 3A thread fit and coarse threading, installation is swift and reliable, minimizing assembly errors. These screws are ideal for applications requiring robust, tamper-proof fastening without compromising on corrosion resistance or regulatory compliance.

Specification Summary & Compliance

This screw adheres to ASME B18.3 specifications, ensuring dimensional accuracy and performance reliability. The UNC 4-40 thread features a Class 3A fit for precise tolerance, with coarse thread spacing facilitating quick assembly. It is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, confirming its safety for use in regulated industries and commitment to environmental standards.