Abstract: The machine includes a modular rotary drum (10) consisting of various individual sections (10a, 10b, 10c, 10d, 10e) each having a frustoconical shape converging in the direction of progression of the objects to be sorted. The walls of the various sections are riddled with calibrated sorting holes (26) the size of which increases from the inlet towards the outlet. The interior walls of the various sections are fitted with plates describing a spiral which guides the charge to be sorted, as it progresses. Each sorting hole (26) is in the form of an elongate slot widening in the direction of progression.