Abstract: A rotary tool assembly including a support shaft with a circular mounting flange mounted on the end of the support shaft and extending radially therefrom to a circular periphery. The mounting flange has a recess in the front face which extends radially inwardly from the outer circular periphery of the mounting flange to an axially extending shoulder which has a machined surface. A circular cutting blade is disposed in the first recess and has front and rear surfaces with a circular central opening extending around and engaging the machined shoulder. A circular clamping ring is disposed in a second recess in the front face of the mounting flange with an outer circular periphery disposed in overlapping relationship with the inner circular periphery of the central opening in the cutting blade to clamp the cutting blade to the mounting plate.