Which of the following processes involves a single cut to separate metal?

The cut-off operation is designed specifically for the purpose of making a single cut to separate metal. This process typically involves a cutting tool or blade that creates a straight, precise cut through the material, effectively slicing it into two parts. The main goal of this operation is to divide stock material or completed parts with minimal waste and high accuracy.

In contrast, grinding is a finishing process that removes material through abrasion, and it involves the continuous motion of the grinding wheel against the workpiece rather than a single cut. Milling is a machining process that uses rotary cutters to remove material, but it can involve multiple passes and is not limited to a single cut. Tapping is a process used to create internal threads in a hole, which does not involve the same separation of material as the cut-off operation does.

Thus, the cut-off operation uniquely stands out amongst the options provided as it specifically entails the action of creating a single cut to separate metal.