Which of the following is NOT a function of layout lines?

Layout lines are critical in the machining process, serving several functional roles to guide operators and enhance accuracy. One significant aspect is that they help identify the areas where machining is to occur, ensuring the operator knows where to remove material. This is vital for maintaining the design integrity of the part being machined. Additionally, layout lines assist in aligning cutting tools with the workpiece, contributing to precision during the cutting process. They also play a role in preventing machining errors by clearly marking areas, allowing for adjustments and ensuring sufficient finishing stock remains for final processes.

However, when it comes to measuring parts within an incredibly tight tolerance, such as 0.0001 inches, this task goes beyond the primary functions of layout lines. While layout lines help in indicating machining locations, precise measurements at that level require sophisticated measuring instruments, such as micrometers or gauges. Therefore, layout lines themselves do not serve the function of providing such high-precision measurements, making this option the one that does not align with the typical roles of layout lines in milling practices.