Abstract: A polygonal cutting blade having a circular arc-shaped groove in a hole includes 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. The blade body has a central hole penetrating through the upper surface and the lower surface, and is centrally symmetrical about a central axis of the central hole. 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 fastening screw for fixing the cutting blade. The circular arc-shaped groove directly faces toward an intersection of the two main side surfaces of the set of positioning side surface. A groove central axis of the circular arc-shaped groove has an offset distance from the central axis.

Abstract: An indexable drilling tool, includes a cutter body, an outer blade and an inner blade. The inner blade is surrounded by a first upper surface, a first lower surface and a first side surface. The first upper surface intersects with the first side surface to form multiple identical inner cutting edges. When drilling, a cutting area of the inner cutting edge as a main cutting edge is located between a central inner point and a central outer point on the inner cutting edge. In a feed direction, an inner convex cutting portion with a maximum cutting depth is arranged between the central inner point and the central outer point. Distances between the central inner point and the inner convex cutting portion and between the central outer point and the inner convex cutting portion in an axial direction are H1 and H2 respectively, which meets the following requirement: 0.9H2?H1?1.1H2.

Abstract: A polygonal cutting blade having a circular arc-shaped groove in a hole includes 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. The blade body has a central hole penetrating through the upper surface and the lower surface, and is centrally symmetrical about a central axis of the central hole. 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 fastening screw for fixing the cutting blade. The circular arc-shaped groove directly faces toward an intersection of the two main side surfaces of the set of positioning side surface. A groove central axis of the circular arc-shaped groove has an offset distance from the central axis.