A device for pivoting the knife in its longitudinal axis and for adjusting the knife depth on knife folding machines having a coupling and brake unit disposed between drive motor and knife drive, for the upwards and downwards movement of the knife bar guided in a housing pivotable in the direction of rotation of the drive, characterized in that in the course of the driving axis there is between drive motor and the coupling-brake unit mounted on the housing an elastically deformable rotary joint and in that a substantially vertically extending guide plate is arranged to be rigid with the machine frame and in that for pivoting the knife there is at the bottom end of the housing a stay bolt, the space-forming length of which is adjustable between housing and guide plate, whereby there is in the upper part of the housing on the guide plate side and parallel with the drive axis, a horizontal pivot arbor which serves as a pivoting axis and in that to adjust the knife depth a substantially vertically disposed setscrew is provided which is in screwthreaded engagement with the pivot arbor and the head of which is rotatably held in a substantially horizontal guide flange in the guide plate and in that at least one locking screw is provided to fix the adjusted vertical knife position, the locking screw being in screwthreaded engagement with the knife bar and having its head resting on the guide plate.