| 摘要 |
<p>Provided is a deep-hole boring throwaway tip of three-time symmetry, which can be applied as a central blade for a drill head to both a whole cutting type and a non-cutting core folding-off type. The deep-hole boring throwaway tip is formed into a thick plate type having such a three-time symmetry that three sections (P1 - P3) divided at a center angle of 120 degrees are identically shaped. The blade edge (1) to confront in the boring direction when the tip is mounted in drill heads (D1 and D2) forms an angle shape corresponding to a first section (P1) with a shorter inner blade (11) and a longer outer blade (12), and the outer blade (12) is constituted of two continuous blade portions of a crest-side outer blade portion (12a) of a smaller outer blade angle (ß1) and a foot-side outer blade portion (12b) of a larger outer blade angle (ß2).</p> |
