Which machining operation is primarily used for removing material in a linear path?

The primary machining operation used for removing material in a linear path is shaping. While milling can also remove material along various paths, it typically employs a rotating cutter that moves in multiple directions, which includes both linear and circular motions.

In shaping, a reciprocating linear motion is employed by the tool, which is moved back and forth across the workpiece in a straight line. This specific motion makes shaping particularly effective for creating flat surfaces, grooves, and contours along straight lines.

Turning, on the other hand, involves rotating the workpiece while a fixed cutting tool moves in a linear manner along its length, but it is not primarily linear in nature as it operates around a rotating axis. Grinding can also remove material but usually focuses on finishing surfaces with very fine abrasives in a more complex path rather than strictly linear.

Thus, when focusing strictly on the operation characterized by a linear removal of material, shaping is the most accurate choice.