| 摘要 |
The purpose of the present invention is to add cutting ability to the vicinity of the center portion of the end face of a tool and ensure that plunge cutting and helical cutting can be carried out with the center portion of the tool while the tool has a configuration equivalent to that of the cutting edge section thereof having a core section. In the cutting edge section (1), which has gashes (8 and 9) between cutting edges (1A and 1A) which are adjacent to each other in a rotation direction, center cutting edges (10a to 10f) facing the rotation axis (O) of end cutting edges (2a to 2f) constituting the cutting edges (1A) are formed close to the rotation axis (O). On the rotationally rearward side of each center cutting edge (10a to 10f) and a respective end cutting edge (2a to 2f) continuing radially therefrom, there is formed an end cutting edge second face (4a to 4f) that straddles both edges, said end cutting edge second faces (4a to 4f) continuing to positions facing the rotation axis (O) or close thereto. A center groove (10A to 10F) that runs across the rotation axis (O), functions also as a rake face for a respective center cutting edge (10a to 10f), and continues to a gash (8) is formed between each end cutting edge second face (4a to 4f) and a respective center cutting edge (10a to 10f) that is positioned rotationally rearward. |
