Which machinery operation involves a reciprocating motion with a stationary tool head?

The operation involving a reciprocating motion with a stationary tool head is planing. In planing, the workpiece is fixed in place while the cutting tool, which moves back and forth in a straight line, removes material from the surface of the workpiece to create a flat surface. This is distinctly characterized by the fact that the tool remains stationary in terms of its orientation while the mechanical system causes the workpiece to be pulled or pushed past it for the cutting process.

In shaping, the workpiece typically moves while the tool is the one that reciprocates. Turning involves rotating the workpiece against a stationary cutting tool, and reaming is used to enlarge or improve the finish of an already existing hole, where the tool rotates but does not reciprocate. Thus, planing is the operation that accurately fits the description of having a stationary tool head while employing a reciprocating motion, making it the correct answer.