| 摘要 |
PROBLEM TO BE SOLVED: To improve rigidity and mechanical strength of a small-diameter ultrahard end mill having a bottom blade with its outer diameter D as small as or smaller than 0.5 mm; to suitably use the end mill for run-on working of an inclined surface. SOLUTION: A blade part 14 is provided with a first tapered part 30 and a second tapered part 32 in series. A tapered half angleβ2 of the second tapered part 32 is 5 degrees or more and less than 20 degrees. Angle proportionβ1/β2, a tapered half angleβ1 of the first tapered part 30 to the tapered half angleβ2, is 0.5 or more and less than 1.0 while length dimension L2 of the first tapered part 30 is less than 7D to the outer diameter D of the bottom blade 22. This provides the predetermined rigidity and mechanical strength, suppresses stress concentration caused by rapid change of a diameter dimension, and also suppresses slack deforming or breakages of a tool. The tapered half angleβ1 of the first tapered part 30 is kept to be small and tolerance of an inclination angle and height of the inclined surface where the run-on working is possible is enlarged. COPYRIGHT: (C)2009,JPO&INPIT
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