This is jjshortcut's mini servo gripper (http://www.thingiverse.com/thing:2415) routerized and adapted for 6.7 mm plywood. I am using a 1.5 mm spiral cutter in 1 mm passes.
It appears to work great mechanically speaking (now need to make that servo shield....). Be sure to get metal gear mini servos instead of plastic geared ones, those are way too easy to destroy.

Note: A further iteration of the design with improved gears can be found here: http://www.thingiverse.com/thing:5034

Cut and assemble. This one is quite straightforward, but be sure to leave a full plywood thickness space between the holder and the geared arms.
Screws are m3x30. Use superglue to block the nuts.

In some future iteration, this design might benefit from real involuted gears.

Have fun!