The author describes the principle of a cutting device with counter rotating cutter bars including cam mechanism. The course of contact force, between the cam surface and roller of the bar is investigated by means of an analogous computer to set up a dynamic model of the drive mechanism and chosen shape of cam. The results of the course of the contact force at the angle of cam rotation = 0-180° and for the revolutions of the cam shaft n = 400 r.p.m.. In conclusion cam mechanism a design is introduced and the results of testing of a functional model of a counter-rotating cutter bar are demonstrated.