I use the Rancilio Rocky, and I'm curious to know if anyone has noticed this with their grinder - Rocky or otherwise. Whenever I have taken it apart to clean the burrs, the resulting grind is quite clumpy. Once the burrs have become embedded with coffee and all bunged up again, it produces a nice free-flowing grind. My view is that after cleaning, the grind collects in the troughs of the burrs, but because the burrs are very clean, friction/weight causes it to release in clumps. Once the burrs troughs become permanently bunged with grinds (which takes some time), the grinds flows out very evenly. Having observed this for a number of years following cleaning of the grinder, it makes me wonder if burrs should not be cut so deep. The tips of the burrs will always remain clean due to the grinding action.
I'm interested to know if anyone has any thoughts on this observation.