CNC Routers

Hi Guys,
I'm gonna jump straight in the deep end here. I have
been looking at 'home made CNC routers' on various forums, and
basically I want to try and build one myself, can anybody give me
some pointers, drawings advice etc,etc. I have access to varied
machines to make parts, and I'd just like to know how to start, I
have loads of time to kill. Any help would be appreciated.
Mark...