Albert,
Use size 23 steppers. Use 1/4-20 rod for a PCB mill.
That board from hobbycnc will be perfect.
Kcam works but is slower than Turbocnc. Steppers don't like Windows, unless you use Mach1.
http://www.artofcnc.ca/
The other end of the rod should be supported in a ballbearing. Find a bearing that fits over the rod you will be using. Tighten a nut on each side. Mount the bearing in a nylon block. This works to keep the endplay down. The motor bearing should not take the side loads.
Here is a pic.
I know of no plans for a larger machine that cuts metal.
Eric