CNC Machine Tool - Prelude

I've been toying with my own CNC machine for nearly as long as I've been an engineer. It's evolved over years and years. I've scanned many of the homebrew CNCs out there, but none were to my liking. Wood has no place in a machine tool. Neither does a Dremel. If you're going to spend so much time and money, do it right. So for the better part of the past decade I've been mulling my own machine tool in my head, sketching ideas, refining them, throwing them out and starting over. It really came down to balancing three things:
1) Money. This thing can't cost me too much. If the price starts to soar, it'd be more economical (and much quicker) to just buy one.2) Abilities/Tools. I could design a column cast of iron, machined to incredible tolerances. But it'd do me no good, as I can't make it. I have to design around things I can do and tools I have (or can easily get).
3) Capabilities. I'm not going to waste my time on a tool that can only machine a pebble sized part. Or one that can only cut to meter tolerances.

Many considerations came into play (and still are bouncing back and forth). First was the configuration. There are dozens and dozens of configurations for machine tools, but what satisfies all three of my stipulations best? I soon learned it was the gantry mill (and soon after I learned that, I discovered that there were sub-configurations I had to figure on). Anyway... A gantry mill is a simple structure that can be built with simple hand tools and simple materials. So far, very few special components had to be found.

Behold! The Gantry Mill!

Well, a partial concept anyway. Simple materials make up the bulk. Square and rectangular tubing make for a great start. Linear guides and ballscrews (bought from ebay. Thankyou cheap Chinese crap!) add great precision and capability. Servomotors would be nice, but don't even look at pricing those, you'll just get depressed. Steppers are an affordable option (and have a few hidden benefits) that provide the control needed. Down the road I plan to play with open-loop feedback (perhaps from a few hacked digital calipers?) for even better accuracy and control.

More to come on the Gantry Mill, The Spindle is currently under construction, and is actually the largest hurdle to production. But, like I said, more on that later...