Which process is described as enlarging an existing hole?

The process that is described as enlarging an existing hole is known as boring. Boring is specifically designed to achieve greater accuracy and a larger diameter in pre-existing holes. This operation typically uses a single-point cutting tool that removes material from the interior surface of the hole, improving its dimensional accuracy and surface finish.

While drilling creates new holes, it is not focused on enlarging existing ones. Milling involves removing material from a workpiece to create flat or contoured surfaces, which does not directly relate to enlarging holes. Reaming, on the other hand, is a precision process used to slightly enlarge holes and improve their surface finish but is distinct from boring in that it is generally used for finishing rather than significantly increasing diameter. Thus, boring is the best answer when the task specifically calls for enlarging an existing hole.