In the context of fasteners, what feature of the cap nut helps prevent contact with external threads?

• A. A double seal
• B. A domed top
• C. A textured surface
• D. A hexagonal locking system

Answer: (B)

The cap nut's design is specifically intended to prevent contact with external threads, and this is primarily achieved through its domed top. The rounded or domed shape of the cap nut covers the end of the fastener, shielding the threads beneath from external elements and potential damage. By having this design, the cap nut not only protects the threads from physical contact but also offers a degree of aesthetic appeal, as it provides a neat finish to exposed fasteners.

The other features listed do not serve the purpose of preventing contact with external threads in the same effective manner. A double seal, for instance, is typically employed in applications requiring the prevention of leaks, and while it might have its own benefits, it is not relevant to the prevention of outer thread contact. A textured surface can enhance grip but does not contribute to preventing contact with external threads. The hexagonal locking system is essential for securing nuts in place but does not prevent contact; instead, it focuses on maintaining the stability of the connection. Hence, the domed top is the salient feature that effectively addresses the issue of protecting external threads from contact.