Cutting head for filter assembler

A cutting head for filter attachment machine comprising a drum carrying a plurality of radially-directed knives each of which is urged radially outwards by two springs at or near the opposite ends of the respective knife so that the knife is freely outwardly movable against a single adjustable retaining device which limits said outward movement and by which the normal distance of the cutting edge of the knife from the axis of the drum can be adjusted, said retaining device for each knife being positioned centrally between the two springs so as to permit pivotal movement of the knife with respect to the cutting head.