A roll grinder is usually installed in aluminium, paper or steel mills to grind textured and smooth rolls. Roll grinding involves external cylindrical grinding between centres. The machined rolls are much larger than conventional workpieces, so they require very large roll grinding machines that can withstand enormous vibrations.
A mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or cutting. Such comminution is an important unit operation in many are many different types of mills and many types of materials processed in them. Historically mills were powered by hand (, via a hand crank), working animal (, horse mill), wind or water ().