Millwright Level 1 Practice Exam

Is the pitch diameter of a thread measured exactly halfway between the major and minor diameters?

1. True

2. False

3. It varies with the thread type

4. Only for specialized threads

The correct answer is: False

The pitch diameter of a thread is not measured exactly halfway between the major and minor diameters. Instead, the pitch diameter is defined as the diameter at which the width of the thread ridge and the width of the thread groove are equal. This measurement is critical for ensuring proper fit and function of mating threads, as it directly influences how effectively threads engage with one another. The major diameter is the largest diameter of the thread, while the minor diameter is the smallest. The relationship between these diameters and the pitch diameter can be defined and calculated based on specific thread forms, including Unified, Metric, and others, rather than being a fixed halfway measurement. In summary, the pitch diameter is a specific and context-dependent measurement, reflecting the nature of the thread design rather than simply being an average of the major and minor diameters. This is why the correct answer indicates that the statement is false.