Which tool is commonly used to find the center of a shaft or other cylindrical work?

A combination set is a versatile tool that includes a ruler and a protractor, often featuring a square head, which makes it useful for a variety of measuring tasks in machining and metalworking. When trying to find the center of a shaft or another cylindrical workpiece, the combination set can be utilized to measure diameters at various points. It allows for the establishment of center lines through careful marking, which aids in the precise location of the shaft's center. The square head of the combination set enables the operator to draw reference lines directly onto the surface of the shaft.

Other options, while useful for measurement tasks, do not specifically address the requirement of finding a center. A caliper set is generally used for measuring distances or dimensions, but it does not provide a means to mark or locate centers effectively. A micrometer is highly accurate for measuring the thickness or diameter of an object but is not designed for marking or establishing center lines. Similarly, a Vernier scale offers precision measurement, yet it does not serve the specialized function of locating the center of round objects. Hence, the combination set is the most suitable tool for this particular application.