A tool, a toolholder and a tool-toolholder unit obtained by coupling tool and toolholder is adapted to be fixed to a rotor of a shredder. The tool and the toolholder have a coupling mechanism that permit a quick and easy assembly or disassembly of the two elements and ensure, at the same time, a stable and safe fixing during use of the tool.

A cutting tool including a toolholder and a round cutting insert for mounting on a pocket floor of the toolholder. The toolholder includes the toolholder pocket floor having a bore and a plurality of grooves in the pocket floor arranged radially about the bore, wherein adjacent grooves are radially offset by a groove offset angle, x. The round cutting insert includes an upper surface having a cutting edge, a lower surface opposite the upper surface, an exterior side surface between the upper surface and the lower surface, an interior side surface defining an aperture extending from the upper surface to the lower surface, and a plurality of lugs arranged radially about the aperture. In an alternate embodiment, the cutting tool includes an anti-rotation disc with a plurality of grooves instead of the toolholder pocket floor.