I need to drill a precise hole into a small cavity which happens to the parallel to the face of the piece of wood. To better illustrate this I made a simple diagram to be absolutely clear on what I'm working with here. The space is too small for me to fit any sort of drill into it. I thought about using a dremel with a flexible shaft attached but I need the hole to be as close to perfectly parallel as possible.
For those who are familiar with guitars, this is a cavity for the springs of a floating tremolo system. I am having a lot of issues with the spring return which has to do with the hole being drilled out incorrectly. I also need to fill the old holes and probably re-drill through them. What is the best method to do this as well?