Machines for making bales of disgregated materials, including a compacting chamber in which a pressing member moves towards and away from a stopping point for compacting the disgregated materials, the chamber having a larger lower surface which has a substantially flat surface provided with runoff holes, smaller surfaces each having a frame which serves as an attachment flange, an output door arranged to move in a vertical direction irrespective of whether the pressing plate has reached the stopping point, wherein the capacity of the chamber is variable to accommodate a possible excess in the disgregated materials introduced into the chamber to be compacted, and a telescopic box having on at least one of its walls through holes located in the proximity of the door.