I used one like that before somebody gave me a proper grinder.
Got the impression slowly shaking / moving the thing up and down helped with a homogeneous "grind".
It was ok for using it in a moka-pot.
Disagree with that, using a bladed unit for the grind, my moka tasted like shit and more often than not got choked until I got the Zass, and now with the Helor it's even better, more consistent.
I used one like that before somebody gave me a proper grinder.
Got the impression slowly shaking / moving the thing up and down helped with a homogeneous "grind".
It was ok for using it in a moka-pot.