Abstract: A coupling for a sheet fed rotary printing machine utilizes a sheet transfer drum having a pair of interfitting toothed drive wheels. The two toothed drive wheels are joined to each other by a friction fit that is applied through a plurality of elongated cylinder screws. These screws are tensioned by a group of radially extending, pivotably mounted actuating levers. A pneumatic cylinder and piston rod assembly is used to release the tensioning force applied to the cylinder screws to thus allow the two toothed wheels and hence the sheet transport component of the sheet transfer drum to which they are attached by be rotated relative to one another. Such relative rotation is accomplished by locking one printing couple and driving the other.