Abstract: A perforating apparatus wherein two rolls define a nip for a running web of paper which is provided with rows of transverse perforations by tools at the periphery of one of the rolls. The rolls are driven in opposite directions by a timing shaft through the medium of a system of gears including an intermediate gear which indirectly drives the one roll and is directly or indirectly mounted on an eccentric. The eccentric is driven by a power train including a differential one output shaft of which carries the eccentric and another output shaft of which is normally held against rotation but can be turned by a worm to thereby change the phase of the one output shaft relative to the input shaft of the differential to thus compensate for eventual inaccuracies in the distribution of perforating tools at the periphery of the one roll.