Millwright Level 1 Practice Exam

What is different about the scale of a depth micrometer compared to a regular micrometer?

1. The thimble measures the depth directly

2. The scale is only used for marking

3. The distance measured is covered by the thimble

4. Depth micrometers have a digital display

The correct answer is: The distance measured is covered by the thimble

The correct answer highlights a key feature of depth micrometers: the distance measured is indeed covered by the thimble. In a typical micrometer, measurements are made by adjusting the spindle and measuring elements that directly contact the dimension being measured. Conversely, a depth micrometer typically has a measuring rod that extends downward from the thimble into a recess or hole. As the thimble turns, it advances this rod further into the space being measured, allowing for the direct measurement of depth. The rotational motion of the thimble indicates how far the measuring rod has extended, thus allowing it to measure depths where standard micrometers cannot, such as in blind holes or recesses. The arrangement ensures that the actual depth being measured corresponds to how far the thimble has moved, making it a specialized tool for different applications than regular micrometers.