Dirk,
Those pictures are very interesting. I can see how how the drill would work but I can't see any Z-axis adjustment except for mechanical stops. It looks like the Z-axis is controlled by an air cylinder and is therefore binary, either up or down (I can't quite tell from the photos whether there is a proportional inlet controlled by a proximity sensor). If I wanted to drill shelf-pin holes 1/2-inch deep and then wanted to drill other holes at some other depth, it looks like I would have to adjust the air cylinder's mechanical stop. Is that the way it works or did I mis-read the photos?