Abstract: An agricultural baler having a main frame, a stuffer for loading successive charges of crop material into a baling chamber installed on the frame and a plunger for compressing the charges into packages of crop material. When the package has reached a predetermined length, a trip mechanism actuates a tying mechanism to tie a series of strands around the package to form a finished bale. The drive line to the tying mechanism comprises a dog clutch assembly including a continuously rotated hub and a dog lever positioned for possible engagement of a cam lobe on the inner surface of the hub. In between tying cycles a lever of the trip mechanism keeps the dog lever away from the hub surface. A timing cam cooperating with a roller on the lever precludes the actuation of the dog clutch when the cam lobe passes in the vicinity of the dog lever.