| 摘要 |
PROBLEM TO BE SOLVED: To prevent blade chipping or breakage due to biting of chips more effectively when a perfect ridge section is screwed in a threaded hole formed by a chamfer section. SOLUTION: Since chamfering 30 is formed in the cutting blade 28 of the shank side ridge section 24b of the perfect ridge section 24, chips are easily pushed out to the peripheral side and entanglement of the chips to the perfect ridge section 24 is suppressed, and moreover, the strength of the cutting blade is enhanced by the chamfering 30. Since the lead of a helical groove 20 is gradually increased toward a groove dead end from a tap front end, the rake angle of the cutting blade 28 of the chamfer section 22 can be enlarged, and excellent sharpness of the blade can be obtained. Moreover, while the chips are curled small, they are guided to the helical groove 20, and discharged to the shank side smoothly. That suppresses entanglement of the chips to the perfect ridge section 24, and prevents blade chipping or breakage due to biting of the chips in cooperation with the existence of the chamfering 30. COPYRIGHT: (C)2009,JPO&INPIT
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