An interfolding machine for production of interfolded packs of sheet articles from strips comprising: - a frame; - cutting means for realising cuts or lines or pre-cutting or tearing perforations on strips so as to produce sheet articles; - a first folding roller for moving sheet articles which rotates with respect to the frame about a respective rotation axis; - first folding fingers for folding the sheet articles moved by the first folding roller which are movable with respect to the frame so as to move away from and towards the first folding roller; - means for transforming a rotary motion in input into an oscillating motion in output which comprise an input shaft and an output which is connected to the first folding fingers so as to move the first folding fingers; - a toothed drive gear which rotates with respect to the frame about a respective rotation axis; - a toothed driven gear which rotates with respect to the frame about a respective rotation axis and which is coupled to the input shaft so as to rotate together; - a toothed belt or a chain which engages the toothed drive gear and the toothed driven gear so as to transmit the motion synchronously; - means for making the first folding roller and the toothed drive gear rotate so that the toothed drive gear rotates in synchrony with the first folding roller; - a second folding roller for moving sheet articles which rotates with respect to the frame about a respective rotation axis; - second folding fingers for folding the sheet articles moved by the second folding roller; wherein the first folding roller, the first folding fingers, the second folding roller and the second folding fingers cooperate with one another to interfold the sheet articles and wherein the position of the first folding fingers with respect to the angular position of the first folding roller is adjustable, the interfolding machine being characterised in that it comprises: - a guide which engages the toothed belt or the chain and which is movable with respect to the frame in such a way as to vary the pathway of one of the branches between the toothed drive gear and the toothed driven gear; - an actuator which moves the guide between a first position corresponding to a first orientation of the toothed driven gear with respect to the toothed drive gear and a second position corresponding to a second orientation of the toothed driven gear with respect to the toothed drive gear in order to adjust the position of the first folding fingers with respect to the angular position of the first folding roller; - control means for controlling the actuator which determine the position of the guide on the basis of the rotation velocity of the first folding roller. - a frame; - cutting means for realising cuts or lines or pre-cutting or tearing perforations on strips so as to produce sheet articles; - a first folding roller for moving sheet articles which rotates with respect to the frame about a respective rotation axis; - first folding fingers for folding the sheet articles moved by the first folding roller which are movable with respect to the frame so as to move away from and towards the first folding roller; - means for transforming a rotary motion in input into an oscillating motion in output which comprise an input shaft and an output which is connected to the first folding fingers so as to move the first folding fingers; - a toothed drive gear which rotates with respect to the frame about a respective rotation axis; - a toothed driven gear which rotates with respect to the frame about a respective rotation axis and which is coupled to the input shaft so as to rotate together; - a toothed belt or a chain which engages the toothed drive gear and the toothed driven gear so as to transmit the motion synchronously; - means for making the first folding roller and the toothed drive gear rotate so that the toothed drive gear rotates in synchrony with the first folding roller; - a second folding roller for moving sheet articles which rotates with respect to the frame about a respective rotation axis; - second folding fingers for folding the sheet articles moved by the second folding roller; - a guide which engages the toothed belt or the chain and which is movable with respect to the frame in such a way as to vary the pathway of one of the branches between the toothed drive gear and the toothed driven gear; - an actuator which moves the guide between a first position corresponding to a first orientation of the toothed driven gear with respect to the toothed drive gear and a second position corresponding to a second orientation of the toothed driven gear with respect to the toothed drive gear in order to adjust the position of the first folding fingers with respect to the angular position of the first folding roller; - control means for controlling the actuator which determine the position of the guide on the basis of the rotation velocity of the first folding roller.