I already have an old rok grinder and I want to upgrade it, but I am not sure what manual grinders are good. The characteristics that I am looking for are mainly: Consistency of grains and general durability.
Most grinders has the handle at top and when grinding it causes inconsistency of grains. For example in all Hario grinders you will see some grain too fine and others too coarse, you can even move the bottom part of the mill sideways with your hand!
One flaw of rock grinder is a part near the bottom made of plastic (at least in old models), its function is to move the grains while grinding. In my case it broke after a few weeks of use.
The methods in which I usually brew coffee are: Chemex, v60 and woodneck. Some times I also brew in aeropress, eva-solo and ibrik. So it is needed coarse grinding for eva-solo and very fine grinding for ibrik