Homebrew PCBs

A resolution of .004" is probably pretty good for a 
particle-board-and-drawer-slide machine.  If you want the fun of making 
your own cartesian robot or just want to non-critical work like engrave 
signs.  For PC Board work, I'm pretty impressed with the Zen Cart 7 by 7 
machine:

http://zentoolworks.com/product_info.php?products_id=74

Check out their user videos and Youtube for some good examples of 
routing PC board with a .1mm cutter with sufficient accuracy for 
double-sided boards.  Not perfect, but it looks pretty good for the 
price, and the PVC frame and actual linear bearing slides will be much 
more precise and dimensionally stable than anything that can be done 
with hardware store components.    I also like that it's an engineered 
system rather than a hodgepodge of whatever was on sale on eBay at the 
time.    Anyone using one who can provide some first person feedback?

73, Bob W9RAN