Steve,
Don't take the plotter apart until you look at:
http://www.qsl.net/ve2emm/pcb/pcbe.html Also, hooking up a Dremel or other tool to a Plotter
has a drawback. Pen-up and pen-down signals are too fast. If
you use a dashpot to slow the solenoid, the X Y will start moving
before the Dremel is down all the way. A plotter can make really
nice boards. It is possible to gut a plotter and drive it using
GCode files. Then using the Z axis movement you can get the timing
right.
John