What type of machining operation is referred to as "turning"?

Turning is a machining operation that involves shaping a material by removing material from a rotating workpiece, typically on a lathe. In this process, the workpiece is set in motion, and a cutting tool is brought into contact with it to remove excess material, thereby creating various shapes and finishes. This technique is commonly used to produce cylindrical parts and components with specific profiles, diameters, and lengths.

The other choices describe different machining operations. For instance, moving material by grinding involves using an abrasive wheel to smooth or shape materials, which is distinct from the rotational aspect of turning. Using a jig to flatten surfaces pertains to surface preparation and finishing operations, not the removal process characteristic of turning. Cutting material into smaller rectangular pieces can refer to various cutting methods, such as sawing or shearing, but does not encapsulate the specific action of removing material from a rotating workpiece as in turning. Thus, the clarity of turning as a distinct machining operation is well represented in the correct choice.