You do indeed have to be very careful in swapping tonearm wands because there is "rotational play" in the armwand with respect to the keying mechanism on the threaded base.
The threads are cut precisely but the keyway has enough play in it so that azimuth is clearly affected. The bottom line is that I wish Bob had been able to design the keying level of fit better so that you don't have to be concerned about azimuth being off when you swap armwands.
I don't swap armwands much because of this. You can verify this by installing the armwand and leaving the knurled knob slightly loose. At this point you can still rotate the wand a few degrees in either direction. Once you have the wand aligned fairly close, you can then tighten it. I don't like to see the arm base tilted to one side by using the azimuth adjustment screw to set azimuth. I prefer to use it only to finetune azimuth ever so slightly.
The threads are cut precisely but the keyway has enough play in it so that azimuth is clearly affected. The bottom line is that I wish Bob had been able to design the keying level of fit better so that you don't have to be concerned about azimuth being off when you swap armwands.
I don't swap armwands much because of this. You can verify this by installing the armwand and leaving the knurled knob slightly loose. At this point you can still rotate the wand a few degrees in either direction. Once you have the wand aligned fairly close, you can then tighten it. I don't like to see the arm base tilted to one side by using the azimuth adjustment screw to set azimuth. I prefer to use it only to finetune azimuth ever so slightly.