Hello! I just went through a nice build log by Moondog. He built a nice, big machine. His machine did use servos, but with different reduction and the right motor sizing steppers would work just as well. What was interesting was that he used a belt drive vs. rack and pinion. Seems simple and rugged. Precise? You be the judge-visit his site and see the boat kits he produces with he machine. The build log is here. His web site is CapeBoatWorks.
Ynneb has also put together a larger machine. Again, servos. I'm not sure if it is rack and pinion or belt driven. He has a web site here , but I think he is still getting it up and going. See his machine in the DIY CNC Machines section, here.
Other than suggesting these links, I'm afraid I can't be of much more help. Good luck!
Resist the urge to do a direct drive rack and pinion or belt drive. While you will have breath taking rapids (something like the earth's escape velocity) your resolution and noise level will be less than impressive. 2000 oz/in.....wow your machine could double as a car crusher (just kidding). With a light gantry and no cutting forces 200 oz-in geared down at 3:1 are plenty for rapids up to 300 or 400 IPM. If you need higher rapids I would recommend looking at servos. I'm sure you have read all the points of steppers vs servos but the major one a lot of people miss is that you are always (in the design process) trading speed for torque. A servo spins and has increased effective torque at 2500 to 4500 RPM depending on the motor. The gear ratios are closer to 6:1 for that speed so using 100 oz-in servos with the reduction gives you the effective torque of a 600 oz-in directly coupled.
Consider using a dual drive on the gantry (you can get by with even smaller motors on each side).
The size of the table only comes into play if it impacts the weight of the gantry. The motors will run down a 30ft slide and easily as a 6ft provided the frictional forces stay constant. Bigger (longer) tables don't need bigger motors unless you want faster rapids (like 1000 IPM) to get to the other end quickly. Even then they won't be 10 times bigger than a normal machine
Thanks for your advice, the only reason I had those 2000oz monsters in mind was that I had the option to buy them cheap. I had pretty much made up my mind to have one stepper on each side of the gantry and to slave/master them in software. Do you know a good place to buy Gears, I have looked at a couple of places but none look that good.