dansig - Here is what another member told me about his experience with the Ergo holder. I have a nerve problem in my left hand and bought one, but now afraid to use it:
Greetings. The holder may indeed help you considering the nerve trouble. What happens is tightening down the set screw aginst the turner, "squeezes" the turner, causing it to cut the neck smaller. On mine it cut .0002" smaller neck thickness, which equates to .0004" total outside diameter reduction. I measure every case after turning with a case neck micrometer, so I caught it right away. How much smaller yours will cut when securing the turner inside the holder will depend on how tight you turn the set screw, at least up to the point the turner no longer compresses together. This will be no problem at all if you clamp the turner into the holder from the start. I had been using mine without the holder and decided to try the holder. Since I had already been turning to finished dimension, I had to readjust the cutter position. This was not a big deal, but could be if you have the dimension set, clamp the turner inside the holder, and then turn dozens of cases without checking the neck thickness. Hope this helps and that my explanation was not confusing.