One other thing to think about in your design. You NEED a way to center the tip on the centerline of the mounting shaft(spindle).

(;-) TP

LoL I was thinking about that right when I chucked it... I need help with some ideas on how to center the probe. One thought was to use a Piezo ring that has a holw in the center, using the hole to bolt the probe to, but I cant seem to think of an easy way to have that adjustable wile assembled. Maybe like four set screws on bottom and on top, tightening two washers together pitching the Piezo... Sloppy but it'd work...

I'm leaning towards the same design as shown, the probe being bolted, or soldered like it is now, to the center of Piezo, then making the ledge where the disk rests slightly large(instead of exact fit like now). The adjustment would be snugging the Piezo retainer(threaded instead of pressed) and  just enough to get a little movement to tap it to center then tighten it down once centered? or have the adjustment just tilting the Piezo slightly maybe....

What do you guys think?