inspired by some models on thingiverse, but upgraded, some changes were made. 
It works great! Honestly haven't find better grinder yet.

Infill 10-15% is more than enough but you can go with more, depends on how you want your grinder to be heavy. Heavier has better feel in your hands :D

But! be sure to use variable inffil . The spikes needs to be printed on 100% infill.

Perimeter 2 is ok, you can try to add more, like 3 or 4 for spikes (haven't tested yet).

After you start using it (first or second grinding, after that it will be ok), pay attention for possibly breaked spikes, always look if there aren't some missing on grinder (you don't want to smoke PLA :D).