Polygonal cutting blade having circular arc-shaped groove in hole and cutting tool

A polygonal cutting blade having a circular arc-shaped groove in a hole, the polygonal cutting blade comprising a blade body composed of an upper surface, a lower surface and a plurality of main side surfaces connecting the upper surface and the lower surface;

• wherein the blade body is provided with a central hole penetrating through the upper surface and the lower surface, and the blade body is centrally symmetrical about a central axis of the central hole;
• the main side surfaces intersect the upper surface to form a main cutting edge;
• in the plurality of main side surfaces, at least one set of positioning side surface comprised of adjacent two of the main side surfaces is provided;
• an inner surface of the central hole has at least one circular arc-shaped groove fitting with a surface of a fastening screw for fixing the cutting blade;
• a number of the circular arc-shaped groove corresponds to a number of the set of positioning side surface;
• each circular arc-shaped groove directly faces toward an intersection of the two main side surfaces of the set of positioning side surface, and a groove central axis of the circular arc-shaped groove has an offset distance from the central axis.