Interesting.
Looking into it, the NEMA23's on my G0704 appear to be 2.2mH and rated for 6.0A.
I am running them with a 48V supply (more or less, this particular supply seems to be open-loop and its voltage varies a bit depending on load, ...).
This metric would give ~47V.
I am generally running them at 20 IPM, with.
IIRC, ~ 10 revs/inch; or ~200 RPM for X/Y; and ~ 32 revs/inch or ~ 512 RPM for Z (IIRC, it was 5 TPI for X/Y with 2:1 reduction, 8 TPI for Z with 4:1); could be wrong here, I am going off memory.
But, as noted, 20 IPM was chosen as this is the speed I could run it at without getting any lost steps during a sequence of rapid moves (would issue a sequence of rapid moves and verify that the mill was still in the expected place).
The 570 oz-in NEMA23's on my lathe are 2.5mH, rated for 5.0A. I ended up running them at a similar speed.
I still haven't extensively tested this, but it appears to work.
There is a 2:1 reduction (due to the lathe's gearbox); working backwards, it seems to be 28 revs/inch, or 14 TPI on the leadscrew (may need to verify), implying ~ 560 RPM.
At 1:1, the torque requirements (to move the carriage) tend to overload the motor (could require closer to ~ 1000 oz-in?).
In both cases, it seems I am running them a bit under their rated current, but then again this limits the motors getting overly warm.
The NEMA34 I am using as a spindle is 5mH (as wired), working out to around 73V.
As noted, it is rated 8.8A, but I am currently running 5.5A (and it runs decidedly warm), but is apparently probably OK (after a few minutes, reaches a temperature of ~ 40-50C or so, then mostly levels off).
The way that the Automation Technologies page said to wire it would make it have 20mH, but whatever voltage the KL-11080 is putting out doesn't really appear to be enough to get particularly high RPMs (this metric gives 143V, and bridge-rectified 110VAC could theoretically give 170V, so dunno...). Extrapolating from other patterns, the driver seems to perform more like it is operating at 70V than would be expected if it were operating at 140-170V.
As-is, running the spindle at 250 RPM, is ~500 RPM on the motor.
If it were 140-170V, I would expect a wider RPM range than this (with a motor at 5mH).
I am not sure the voltage the driver is putting out (whatever it is putting out is seemingly something the multimeters I have are unable to deal with, granted all I have on hand are the Harbor Freight / Cen-Tech DMMs).