An abrasive rotary tool includes a tool shank a flexible planar section positioned opposite the tool shank. The flexible planar section forms a first abrasive external surface on a first side of the flexible planar section and a second abrasive external surface on a second side of the flexible planar section. The flexible planar section facilitates abrading, corners of a workpiece across multiple angles relative to the axis of rotation for the rotary tool through bending of the flexible planar section when the abrasive external surfaces are applied to a corner of the workpiece.