Abstract: A rotary grinder employing blades is disclosed, which comprises a substantially cylindrical rotor, on the periphery of which is mounted, along certain regularly spaced apart generatrix lines, a plurality of identical blades of short length with respect to the length of the rotor, wherein the blades are disposed at a rate of one blade per generatrix line and so that two blades located on adjacent a generatrix lines present therebetween, longitudinally, a distance approximately equal to or greater than a length of blade.