What operation separates a finished part from the remaining stock on a lathe?

The operation that separates a finished part from the remaining stock on a lathe is the cutoff. This process typically involves a cutting tool that effectively slices through the workpiece at a predetermined point, allowing the completed part to be removed cleanly from the unmachined material. This is particularly important in lathe operations where the raw material (stock) is gradually reduced to achieve the desired shape and dimensions of the finished part.

Turning, facing, and drilling are all essential lathe operations, but they serve different purposes. Turning involves cutting away material to achieve the desired shape, facing creates a flat surface at the end of a workpiece, and drilling creates holes through the material. None of these operations are specifically designed to separate the finished component from the leftover stock, making cutoff the correct choice for that specific task.