Green coffee is graded by size. This is performed mechanically, with multiple layered screens, which allow coffee to fall through as it is vibrated forward.
Each screen has different size perforations, from 12 to 20 for round beans and 8 to 13 for peaberry, which translates to (that #/64 of an inch).
Coffee is then channeled into a separate chute, where it continues processing for density and defects.
