| 摘要 |
PURPOSE: To exhibit excellent cutting performance at the threading of a titanium-based alloy-made workpiece by forming the chip surface adjacent to the cutting edge of a cutting screw part so as to have a negative rake angle. CONSTITUTION: The core constituting the inner part of this threading tap is formed of tool steel. A thick cover is provided on the outside of the core. The cover is formed of a Fe, Co and/or Ni-based metallic base material and 30-70 vol.% of a ultra-fine particle material in the form of carbide, nitride and/or carbonitride of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and/or W. This hard material has a grain size <1μm, preferably, a grain size <0.5μm within the base material. The cutting edge 12 of the chip surface 13 of a cutting screw 9 in this threading tap has a negative rake angleα. |
