What should be limited when using a center punch to prevent damage?

When using a center punch, it is crucial to limit the amount of force applied to prevent damage to the material being worked on. If excessive force is used, it can lead to deformation, cracking, or other forms of damage that can compromise the integrity of the aircraft structure. A controlled and appropriate amount of force ensures that the center punch creates a small, effective indent that guides the drill without risking the structural integrity of the surrounding metal.

In this context, the other options do not directly address the potential for damage in the same way that force applied does. Tracking time spent or the angle of impact may be considerations during the operation but are less critical to preventing damage as compared to the amount of force. Similarly, while the depth of the impression should be monitored, it is the force that primarily dictates the risk of damage. Controlling force is therefore essential in maintaining the quality and safety of the aircraft's metal structure.