Threading with A B phase only?

A 1600oz/in NEMA-34 motor may not be any faster than a 1090oz/in NEMA-34 motor. In fact, all other things being equal, it will more than likely be slower. (It will only be more powerful at or near 0 speed.)

This was why I recommended the closed-loop motors. They make the same torque, but run faster (and shouldn't lose steps)

Ah well thank you both of you - this is all a very interesting learning process for me and I am grateful for your advice. So what is the advantage of a more powerful motor?? I am thinking more power on the longitudinal axis enables heavier cuts and smoother threading....albeit as you now tell me not faster?

Sorry for the confusion. If you want better performance the key will really be the ballscrews. This machine was never designed for full contouring only one axis motion at a time thats how they got away with using leadscrews. Just having a bigger or faster motor really won't help you. The problem with moving faster with the leadscrew is backlash; when you change directions at a much higher speed it just sounds horrible and is really hard on the machine. A more powerful motor really won't help you much either because the machine wasn't really designed for heavy cutting. If you push it to hard you will just end up pulling the headstock out of alignment. The nema34 1600oz should work fine and will probably give you about the same performance. The DQ860MC drive is the same one I have, and so far its performed pretty well. Also keep in mind when using leadscrews you will have to plan you toolpath to avoid direction changes while cutting. If you don't you will end up with gouges in your part.

Ok understood thanks Andy.

My latency test gives a figure around 50k-60k - not very good but is that about as good as i can expect from a Dell Optiplex 760 with Intel core 2 duo 3ghz, 4 gb RAM, Intel integrated graphics? If so, then I suppose slow leadscrew is going to be better for me than quick....Are there some tweeks in wheezy that will bring the latency down or is the only thing to get a separate graphics card installed?