Clearly the allowable misalignment is inversely proportional to the speed...as you said in the previous post misalignment absorbs power from the motor, in this case through friction. Since steppers are, relatively speaking, such low power motors this is obviously bad, even if the coupling does tolerate it in reality. I'm sure the manufacturers are conservative with the ratings. Hmm, I'm stating the obvious now, tend to make my own anyway.

This is much more interesting:

http://www.youtube.com/watch?v=G2DU1...ture=endscreen