Hold the burr holder under hot water and it will expand enough to let the burr fall out. Got an order of burrs in from Italy and they all ran large until the next order to straighten it out. Techs found that running the upper burr holder under hot water would expand it just enough to let the burr drop in and out depending on the operation. Thermal coefficient of expansion to the rescue.
Grinders are one of the keys to exceptional espresso. Discuss them here.