In depth machining, which tool is primarily used to mark measurements on a workpiece?

The correct choice is the scriber, which is specifically designed for marking precise measurements and lines on various surfaces, particularly metal and wood. The pointed tip allows for a clear and accurate incising of lines that can guide subsequent machining processes such as cutting, drilling, or milling. This is essential in ensuring that the dimensions of the workpiece are accurately followed.

Scribers typically produce a fine line that remains visible even after other operations, which is crucial in maintaining accuracy throughout the machining process. While calipers and dividers also play important roles in measurement, their primary functions are to measure distances and dimensions rather than directly marking on the workpiece. A pen, while capable of marking, does not provide the precision required for machining tasks, especially when dealing with hard materials where a more durable marking solution is needed. Thus, the scriber's design and purpose make it the best tool for marking measurements in depth machining.