Millwright Level 1 Practice Exam

If a thread is designated 5/8 - 11 Class 2A, what does this indicate?

1. It is a fine pitch thread

2. It is an internal thread

3. It is an external thread

4. It is a special thread

The correct answer is: It is an external thread

The designation 5/8 - 11 Class 2A provides specific information about the type of thread. In this case, the "5/8" indicates the nominal diameter of the thread, which is 5/8 of an inch. The "11" refers to the number of threads per inch, indicating that this is a coarse pitch thread rather than a fine pitch. When "Class 2A" is mentioned, this indicates a certain standard for fit, which is typically applied to external threads. This classification uniquely identifies the thread as an external thread. External threads are those that are formed on the outside of a cylindrical object, whereas internal threads are located on the inside of a hole or a tube. Thus, recognizing the external nature of the thread based on the Class 2A designation helps in applications where joining components is vital. The other options do not apply here. The thread is not fine pitch, as indicated by the "11," which suggests it has a coarser profile. It is not an internal thread because the classification clearly refers to external fit. Lastly, while some threads can be classified as special for various reasons, this designation adheres to standard classifications for regular threading.