| 摘要 |
<p>Disclosed is a double angle drill (10) having a double angle point, wherein the radial rake ? of a leading edge (28) is in the range of 18°-38° and is sufficiently large as compared with the radial rake in a conventional drill (normally, 10° or less), therefore finish processing from burnishing to cutting is performed by the leading edge (28) and poor accuracy of hole diameter is limited regardless of wear of a second cutting edge (18b). Since the rake angle of the second cutting edge (18b) becomes large because the radial rake ? of the leading edge (28) is made large, cutting performance of the second cutting edge (18b) is enhanced and an excellent quality of the processed hole can be attained. Consequently, an excellent quality of the processed hole is attained even in case of drilling a hole in a hard-to-cut material such as FRP, and the lifetime of a tool is enhanced.</p> |
