Abstract: A cutter blade mounting for a rotary mower of the type having a disc carrying two or more blades. The blades are each mounted on a plurality of arms which are pivotally connected at one end thereof to the disc. At the swingable ends of each arm there is a stepped shaft member. The blades are each provided with an aperture to fit over one of the steps of each shaft; and the disc is provided with a plurality of apertures to fit over a second step of each shaft. A blade is inserted in the space between the swinging end of the arm and the disc. Then the arm is swung toward the disc, the one step of the shaft seating in the aperture of the blade and the second step seating in the aperture of the disc. The arm is then secured by fastening means against swinging which in turn clamps the blade to the disc.