★★How to prevent affecting existing holes when drilling deeper

Issue:

It is easy to remove a existing thread when drilling a properly sized countersink at the bottom of the thread,  how to prevent it?

Solution:

1. Untick the Extend start command in Settings when drilling a deeper countersink.
   
2. The effect is as follows.
   
3. You can also untick this command when the top of the hole extends beyond the selected reference surface.