Questions about making a vinyl cutter...

Hi everyone!

I've been lurking around here for a couple of months and its been
interesting. I decided to make a small plotter for a project so I
could have an excuse to use my machine tools more =) Well anyways, I
wanted to make it a pen style plotter, simple. Then I thought, why
not make it so that it can cut vinyl also? So I started searching the
net and I can't seem to find out in detail how a vinyl cutter cuts
the vinyl! I also can't figure out what the blades look like, how
they are mounted, and how much torque is required from the motor to
pull the blade through. If anyone could help me out with these
problems, that would be great! Thanks for your help!

-Chris