I thought I had an oscilloscope but it was a cheap thing I got off amazon for basic circuit testing and proved to be a worthless pile of junk. I do have to get another at some point so perhaps now is the time to do so. I have verified the steps per rev is set to 2000 so that's not an issue unless the driver is not outputting the steps according to it's own datasheet (insert need for oscilloscope). Even if that were the case though, the non-linearity is based on observation of behavior. I don't have my data points handy so I'll have to dig them up this evening or recreate the experiment to verify what I believe I saw before. Of course, now you have me thinking about it, my method for measuring the rotational output wasn't terribly precise at first and got better the more I played with it so perhaps my belief in the non-linearity of the scale value is nothing more than poor testing methods. Regardless of that, the basic issue of the published math to determine scale not working does remain. The math tells me very simply that I should have a scale of 222.222222 (unless I screwed that up?) for a 1.8° per step motor, with 10 microsteps, spinning 40 times for 1 revolution of the dividing head (200*10*40 / 360). I am currently at about 2840 to get the appropriate response from the stepper. This is the same behavior I got from the previous driver and steppers before they all burned up so it doesn't appear to be limited to my current setup.