| 摘要 |
A large-diameter tap cuts a thread in the sides of a commensurate pre-drilled hole. The tap has a large-diameter tool-shank (1) translating to a narrower cutting shank (I). The cutting shank is sub-divided into a first cutting (4) thread (A1) which is esp. separated from a second cutting (4) section (A2) by a third section (B) bearing no cutting thread.
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