Which thread classification uses threads per inch and nominal diameter?

• A. Metric Thread Classification
• B. American/U.S. Thread Classification
• C. Unified Thread Classification
• D. British Standard Thread Classification

Answer: (B)

The American/U.S. Thread Classification is based on the measurement of threads per inch and nominal diameter, which is integral to its specification. This classification system utilizes inch-based measurements, appealing to engineering and manufacturing practices common in the United States.

In this system, the nominal diameter is identified in inches, and the threads are counted per inch of length. This method not only allows for precise definitions of thread characteristics but also aligns with the broader imperial system used in many industries within the U.S.

For comparison, the Metric Thread Classification utilizes a system that measures diameters in millimeters and specifies the distance between threads in millimeters as well. The Unified Thread Classification, while similar to the American system, incorporates both metric and Imperial thread dimensions, making it different from purely American classifications. Lastly, the British Standard Thread Classification has its own standards, primarily focusing on British engineering practices, and uses a different approach for thread specifications as well. This helps clarify why the American/U.S. Thread Classification is the unique system that employs threads per inch along with nominal diameters.