Good morning,
I have a question about my rapid speed. I can only get about 20 inches per minute before my motors start to break up or stall. I am using a Xylotex 4 axis kit with 425 oz-in motors and 1/2-10 ACME thread. The motors react like this without any load as well. Every motor reacts the same, but I don't really know how to address the issue. The machine works great, but travel is very, very slow. Perhaps I am expecting too much, but it seems like everyone else has much better speed than I. Please advise.

That's a common problem with the Xylotex. If you have dual shaft motors, one solution is to buy or build a damper to eliminate mid band resonance, which is most likely your problem.
Another option is to switch to 2 start acme screws, 1/2-8 or 1/2-10, which will just about double your speed, but you'll still probably have resonance issues. I've seen a lot of posts saying that those motors can not be spun very fast with the Xylotex, due to resonance issues. The damper should haelp a lot.

http://www.cnczone.com/forums/showthread.php?p=256639#post256639

Thanks, I am going to start making a set of these right now! Is there anything I can do with micro-stepping to help out with the resonance issue?

You can try the different settings, and they may make a difference, but you'll need to try to see if it helps.