What tool is primarily used for enlarging drilled holes to a desired size?

The tool primarily used for enlarging drilled holes to a desired size is the reamer. Reamers are designed to refine the diameter of a hole, improving its size, shape, and finish. They help achieve precise dimensions and a smoother surface than what can typically be achieved through drilling alone.

In contrast, a tap is used for cutting threads inside a hole, allowing for fasteners to be securely screwed into the material, but it does not enlarge holes. A torque wrench is a tool used to apply a specific torque to a fastener, ensuring that it is tightened to the correct specification, and it does not alter the hole size. A monkey wrench, typically used for gripping and turning nuts and bolts, has no function related to altering the size of holes. Thus, the reamer is the only tool mentioned that serves the purpose of enlarging holes to specific dimensions, making it the appropriate choice.