crushing rolls

1. [img_assist|nid=12002|title=|desc=|link=none|align=right|width=280|height=146]Crushing
   rolls which break material by pressure continuously maintained between
   the faces of two revolving metal cylinders, with axes parallel to each
   other and separated by a space equal in size to that of the required
   finished product; used as fines crushers or for low reduction primary
   crushing of material of a friable and low-abrasive nature.
2. Sledging
   rolls employ a combination of impact, shear and pressure. They have at
   intervals round the rolls, rows of teeth of varying length which grip
   the rock and feed it into the crushing chamber, also acting as picks to
   break the larger lumps; the optimum type of feed is stratified friable
   rock.

Also: roll crushers