In a machine for counting bars, for example metal bars, that are to be sent on to a packaging station which packages a pre-set number of them in bundles, the problem of precise counting of the bars is solved by using, for the conveyance of the bars to the counting station, a screw conveyor, in which each groove of the screw has a wall having a pitch increasing more rapidly as compared to the normal pitch of the screw, thus making it possible, in the case where more than one bar is present in the same groove, to render the lying plane of the bars not parallel to the specific axis of the counting means. This is obtained by providing one of the faces of the grooves either with a special step having a continuously increasing width, or with a continuously increasing inclination.