pinions engage a rack 28 mounted on the frame 30 rotation of the pinions will laterally position the brackets and drum units where desired it will be understood that other lateral adjusting mechanisms could be employed such as threaded members as illustrated in fig4 the drum units such as 16 are comprised of drums 33a and 34a the drum knife 31 and circular plates 45 and 46 which support the knife 31 between the drums 33a and 34a for this purpose an axial clamping means such as a tightenable bolt not shown extends through the center of the drum unit the drum unit can be disassembled and the drums 33a and 34a can be changed in location as shown in fig5 thereby changing the position of the drum knife 31 also the plates can be stacked in different arrangements with additional plates added or plates of different thicknesses to change the position of the drum knives and thereby attain additional variations in spacing for example in fig2 the drum units 16 and 19 are shown with the narrower drums 47 and 48 adjacent each other and the wider drums 49 and 50 located inwardly from the ends of the drum units by reversing the position of the drums 47 and 49 and or reversing the position of the drums 48 and 50 we seen that the position of the knives 32 and 51 will be changed relative to each other this increases the flexibility of the spacing of the knives for slitting sheets of various widths exact adjustment is of course.