Matching Pairs GRINDING MACHINESOnline version Types of Mills by Jhony Guillermo Montesinos Cossio 1 High Pressure Roll Mill 2 Ball Mill 3 SAG Mill 4 What is a mill? 5 Autogenous Mill 6 Rod Mill It is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many processes. It is an acronym for semi-autogenous grinding that also uses grinding balls like a ball mill.