| 摘要 |
PROBLEM TO BE SOLVED: To provide a helical broach for machining an internal gear, improving work helix form accuracy by eliminating deterioration of work helix form accuracy due to finishing of acute-angled tooth flank side of a former half part when the former half of a cutting part of a tooth thickness rise shell finish-cuts a work taking an obtuse-angled tooth flank as a guide using an acute-angled finishing edge, and in the rear half, an obtuse-angled finishing edge finish-cuts the work taking an acute-angled tooth flank as a guide using an obtuse-angled finishing edge immediately after the acute-angled finish edge performs finish-cutting. SOLUTION: When the front half 2a of the cutting part of the tooth thickness rise shell cuts a work using the acute-angled finishing blades T1 to T8 and the rear half 3c' of the tooth thickness rise shell cuts the work using the obtuse-angled finishing edges T9 to T17, as shown in Fig. 3(a), an acute-angled start finishing blade T11 is disposed in a longer span than the work cut length (w) in the rear of the final acute-angled finishing edge T8, whereby the final acute-angled finishing edge T8 and the obtuse-angled cutting start finishing edge T11 are prevented from machining the work at the same time. COPYRIGHT: (C)2007,JPO&INPIT
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