bookbinding machine with a horizontal turntable 2 which carries pairs of clamping jaws and transports the pairs of clamping jaws past work stations , wherein a disc cam is provided coaxially with the turntable to open and close the pairs of clamping jaws , characterized in that the axis of the turntable is defined by a shaft which is rotatably connected with the turntable by friction elements , that the shaft is non - rotatably connected with a second disc cam which controls the movements of a restrainer into and / or from the path of the turntable in order to arrest briefly the turntable whenever a pair of clamping jaws is located at the inserting station for inner books .