| 摘要 |
Because a paired first helical flute (24) and second helical flute (26) that are provided on the drill body (12) of an indexable drill (10) are mirror-finished by machining using ball end mills (30, 32) after being subjected to hardening heat treatment, friction of the inner flute surface is reduced and swarf is favorably evacuated. As a result, abrasion, blade chipping or breakage, etc., which arise from swarf clogging, are limited even in indexable drills (10) with long flute length (L) that are for drilling deep holes and durability (tool life) is improved. Moreover, stable drilling is made possible by a limitation of the increase in cutting resistance due to swarf clogging and the range of possible processing is expanded by a relaxation of the limiting processing conditions under which drilling is possible. |
