Summary

This is a work in progress. I still have many tweaks to be made and is not ready for primetime.
I'm posting it to get input and seed some ideas.

So basically it's designed to run spring loaded on the Z axis of a milling machine and use a limit switch to signal the cam software that the milling bit is in contact with the copper clad board. I just redesigned the locking collar, since the first one was too tight. I have not printed it yet, but it's a portion of the vacuum collar, so should be good. I got the v-slide close, but I need to close up the gap a little and fix the limit switch mounting.
The threaded tube is used to adjust the cutting depth and track the surface of the copper clad board. If you ever want consistent cutting depth you have to either map the whole board and add offsets to your z-axis g-code numbers OR follow the contour. You can get away with course z-axis settings if you can get away with greater then say 16mil traces, but if you want 8-10mil traces you've got to track the surface. The larger the PCB you're attempting the larger the error without tracking or mapping. I added a vacuum port, since there is no escaping the depth collar for millings. I may add intake slots on the depth collar to get better air flow.

I used this motor and collet first:

http://www.ebay.com/itm/Mini-Hand-Drill-DIY-Lathe-Press-555-Motor-w-1-8-Chuck-Mounting-Bracket-12-24V/361989772460?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

But I want to try this one:

http://www.ebay.com/itm/1-5-3-17mm-Collet-Electric-DC12V-Motor-Drill-with-24-Twist-Drill-Bits-Wrenches-/391804304064?hash=item5b395b3ac0:g:UIYAAOSwKytZMsXk

next, so I can shrink the depth gauge collar to track less surface, yielding a smaller averaged area.

It's still an unknown regarding run-out which is my next worry for cutting wobble.

More work to be done!