Abstract: An insert clamp secures a cutting insert having a central hole to a tool holder. The clamp includes a forward protrusion to be received in the central hole of the insert, a central body portion provided with a pressing part to press down the upper surface of the insert and a screw hole for a clamping screw to pass through, and a rear protrusion having a rear contact surface to come in contact with a rearward slanting surface of the tool holder. The forward protrusion is formed on the forward end of the insert clamp, an inside surface of the forward protrusion extends downward in a spaced state apart from the inner wall of the central hole of the insert, and a distal portion of the inside surface the forward protrusion is provided with a protuberance of convex curved surface to come in tangential contact with the inner wall of the insert.

Abstract: A cutting insert has an upper surface, a lower surface, a plurality of side surfaces connecting the upper surface and the lower surface and a central hole formed at a central portion thereof. The cutting insert has a flat seating surface formed on a highest level of the upper surface, a plurality of side cutting edge portions formed at intersections of the upper surface and the side surfaces, and a corner cutting edge portion formed at an intersection of two adjacent side cutting edge portions and having a cutting edge formed at a front end thereof. A land portion, a downward inclined surface, a corner bottom surface, a first protrusion, an upward inclined surface and the seating surface are formed on the corner cutting edge portion sequentially along a diagonal line directed from the cutting edge to the central hole.

Abstract: An insert clamp secures a cutting insert having a central hole to a tool holder. The clamp includes a forward protrusion to be received in the central hole of the insert, a central body portion provided with a pressing part to press down the upper surface of the insert and a screw hole for a clamping screw to pass through, and a rear protrusion having a rear contact surface to come in contact with a rearward slanting surface of the tool holder. The forward protrusion is formed on the forward end of the insert clamp, an inside surface of the forward protrusion extends downward in a spaced state apart from the inner wall of the central hole of the insert, and a distal portion of the inside surface the forward protrusion is provided with a protuberance of convex curved surface to come in tangential contact with the inner wall of the insert.

Abstract: A cutting insert has an upper surface, a lower surface, a plurality of side surfaces connecting the upper surface and the lower surface and a central hole formed at a central portion thereof. The cutting insert has a flat seating surface formed on a highest level of the upper surface, a plurality of side cutting edge portions formed at intersections of the upper surface and the side surfaces, and a corner cutting edge portion formed at an intersection of two adjacent side cutting edge portions and having a cutting edge formed at a front end thereof. A land portion, a downward inclined surface, a corner bottom surface, a first protrusion, an upward inclined surface and the seating surface are formed on the corner cutting edge portion sequentially along a diagonal line directed from the cutting edge to the central hole.