A technical dictionary of printmaking, André Béguin.

Machine in which the offset printing plates are given a surface grain by the impact of small steel balls or pebbles driving an abrasive against the plate.

Polymetaal owns such a machine, and can supply grained aluminium plates in different grains and sizes.
FR. granoir à billes; machine à grainer des plaques offset. German; Kornmaschine, Plattenkornmachine. Dutch; greinmachine, knikkerbak.