S-91221A178 4-40 x 5/8" UL 94 HB Plastic Socket Head Screws

Key Features & Benefits at a Glance

• Exceptional chemical and corrosion resistance from glass-filled nylon construction, ideal for harsh industrial environments.
• Reliable performance across a wide temperature range (-20°F to 230°F), ensuring stability in varying operational conditions.
• Superior assembly efficiency with a fully threaded design and standard UNC coarse threads for faster installation.
• Precise and secure fastening guaranteed by the Class 2A thread fit, minimizing the risk of cross-threading.
• High-strength, lightweight alternative to metal with excellent durability and electrical insulation properties.
• Enhanced safety and compliance meeting UL 94 HB flammability rating, RoHS 3, and REACH environmental standards.
• Easy installation with standard hex drive (3/32") and socket head design, allowing for high torque application in confined spaces.

Professional Applications & Engineering Value

This glass-filled nylon socket head cap screw is engineered to solve critical challenges in industries where metal fasteners fall short. Its black, glass-reinforced plastic construction provides excellent resistance to chemicals, fuels, and solvents, preventing degradation in aggressive environments. The 4-40 UNC coarse thread and Class 2A fit ensure reliable engagement and vibration resistance, reducing maintenance needs in assemblies. With a temperature range of -20°F to 230°F, it performs consistently in applications from electronics enclosures to automotive components, offering a non-conductive, lightweight solution that eliminates galvanic corrosion risks. The fully threaded design maximizes grip length, making it ideal for securing panels, brackets, and machinery parts where thermal stability and regulatory compliance are paramount.

Specification Summary & Compliance

This screw adheres to UNC coarse thread standards with a Class 2A thread fit for consistent dimensional accuracy. It is manufactured to meet UL 94 HB for flammability resistance and is fully compliant with RoHS 3 (2015/863/EU) and REACH (EC 1907/2006) regulations, ensuring it is free from hazardous substances. The product conforms to standard inch measurements for head diameter (0.183"), head height (0.112"), and length (5/8"), providing reliable performance in industrial fastening applications.