A drill worn margin will:

A worn margin on a drill primarily affects the cutting efficiency and dimensional accuracy of the drilled hole. When the margin of the drill is worn, it loses its ability to effectively control the diameter of the hole being drilled, often leading to a scenario where the drill does not remove enough material. This results in the drilled holes being smaller than intended, hence drilling undersize.

The margin acts as a guiding surface that helps to stabilize the drill during operation. When it is worn, this stability is compromised, leading to increased deflection and less precise hole dimensions. Although the other options may seem relevant at first glance, they do not accurately describe the direct consequence of a worn margin. For example, a worn margin does not automatically lead to an increase in hole size, nor does it produce smoother finishes or eliminate the need for finishing tools. Instead, it typically leads to issues with hole size accuracy, emphasizing why the correct choice focuses on drilling undersize.