| 摘要 |
PROBLEM TO BE SOLVED: To provide a tap for working a material hard to be cut such as a metal matrix composite(MMC) into a screw hole and remarkably improved in a service life thereof and formed into a shape hard to be broken by forming the tap into a shape capable of reducing the cutting resistance and forming a diamond film or a diamond-like carbon film hard to be peeled at a cutting part. SOLUTION: The cutting blade part is formed of an imperfect thread shape chamfer part and a perfect thread shape screw part, and this cutting blade part is coated with the diamond film or the diamond-like carbon film. The cutting blade part is divided into four or more linear grooves in the circumferential direction, or the cutting blade part is provided with a spiral groove. Furthermore, a cutting angle of the cutting blade is set from -1 degree to -10 degree, desirably, from -3 degree to -5 degree.
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