| 摘要 |
PURPOSE:To improve the hardness of a tool main body while securing a tip fastening allowance and the accuracy in the deflection quantity of a cutting edge, by forming a soft part whose hardness is lower than that of the tool main body at the bottom face side of the tip fitting seat of the tool main body and machining a screw hole thereon. CONSTITUTION:A through hole 17 whose one end is opened for a bottom face 14 and whose other end is opened for the tool outer peripheral face is formed at the bottom face 14 side of a tip fitting seat 12. At the back of the bottom face 14, a fitting hole 18 extending in the tool axial line direction, whose one end is opened for the tool tip face and whose other end is crossed with the through hole 17, is formed and cylindrical bushes (soft material) 19 are embedded in these fitting holes 18. Moreover, it is preferable to provide the bush 19 freely detachably from the tool main body 11 in order to facilitate the maintenance control of a screw hole 20. The screw hole 20 can easily be worked even in case of the tool main body 11 being subjected to a heat treatment to a high hardness, because it is formed by the material of a lower hardness than that of the tool main body 11. |
