Intro to Millwright Practice Exam

Which type of nut has internal threads that only pass through a portion of the fastener?

1. Hex Nut

2. Cap Nut

3. Lock Nut

4. Wing Nut

The correct answer is: Cap Nut

The correct choice is a cap nut, which is also known as a acorn nut or dome nut. This type of nut features internal threads but is designed so that those threads do not extend the full length of the nut. Instead, the threads only pass through a portion of it, allowing for a smooth, rounded top that covers the end of the fastener. This design not only provides a finished appearance but also protects the threaded end of the bolt or screw from damage and reduces the likelihood of snagging. The other choices each have distinct characteristics that differentiate them from the cap nut. A hex nut has full internal threading that passes entirely through the nut, allowing for comprehensive tightening on the full length of a bolt. A lock nut, which is intended to prevent loosening due to vibration, also has full threads and is typically thicker or has special features such as nylon inserts. A wing nut is designed for hand tightening and features wing-like protrusions, but it also possesses complete threading throughout. Hence, these types do not fit the description provided in the question, making the cap nut the appropriate answer.