S-99477A108 4-40 x 1/2" ASME B18.3, UL 94 HB Plastic Socket Head Screws

Key Features & Benefits at a Glance

• Superior chemical and moisture resistance from polypropylene plastic construction, ideal for corrosive environments and washdown applications.
• Reliable assembly integrity with a Class 2A thread fit, ensuring consistent engagement and reducing the risk of cross-threading.
• High-strength performance for plastic components, offering a robust 4500 psi tensile strength suitable for various light to medium-duty applications.
• Wide operational temperature range from -20° to 180° F, providing dependable performance in diverse thermal conditions.
• Streamlined installation and removal with a standard hex socket drive (3/32"), allowing for efficient torque application with common tools.
• Guaranteed dimensional consistency through compliance with the ASME B18.3 standard, ensuring interchangeability and fit.
• Safe for regulated industries as it is RoHS 3, REACH, and UL 94 HB compliant, meeting strict environmental and safety standards.

Professional Applications & Engineering Value

This 4-40 UNC socket head cap screw is engineered to solve critical challenges in electrical enclosures, medical devices, and food processing equipment. Its polypropylene plastic body is inherently non-conductive and resistant to a wide range of chemicals, preventing galvanic corrosion and making it perfect for sensitive electronic assemblies. The coarse UNC thread and Class 2A fit provide fast, reliable engagement in plastic and soft metal tapped holes, reducing assembly time and minimizing thread stripping. The hex socket drive offers a clean, flush finish and superior torque transmission compared to slotted heads, which is essential for applications with limited space and a need for a sleek profile. This combination of material properties and precision engineering delivers long-term reliability in demanding industrial and commercial applications.

Specification Summary & Compliance

This fastener adheres to precise dimensional standards, including a Class 2A thread fit for unified coarse (UNC) threads, ensuring consistent performance. It is manufactured in compliance with the ASME B18.3 specification for socket head cap screws. The product is fully compliant with RoHS 3 (2015/863/EU), REACH (EC 1907/2006), and meets the flammability rating of UL 94 HB.