通过防旋转的三角形横截面的键56和键槽54处于通过相互面接触紧密接触，由于芯片14被安装在一个恒定的相位，以一体的主体12中围绕主体12，高安装轴线O 获得具有（旋转处理过程中断裂强度）的强度，因为它简单地通过提供主体12和相对表面50和52的芯片14的键槽54的三角形横截面，防旋转键56，生产成本结构简单 有减少。 的润滑油通过设置在安装螺钉80，在芯片14的基端侧的基端侧排出通道中的流体导入路90导入到芯片14侧（径向孔92，间隙66） 和润滑油从设置在芯片14（径向孔94，96，间隙98，该径向槽70），由芯片14的内螺纹的前端侧两者的前端侧排出通道排出到外周侧 是在断裂强度润滑油被充分地供给到进一步改进的加工区域堆积。

By triangular section of arresting the key 56 and keyway 54 are adhered to by surface contact with each other, since the chip 14 is attached to the integrally body 12 with a constant phase in the axis O around the body 12, a high mounting strength with (breaking strength at the time of rotation processing) can be obtained, for good only by providing the body 12 and the opposing surfaces 50, 52 in a triangular cross-section of the key groove 54 of the chip 14, anti-rotation key 56, manufacturing cost structure is simple There is reduced. The lubricating oil is introduced to the chip 14 side through the fluid introduction path 90 provided on the mounting screw 80, the base end side discharge passage provided on the base end side of the chip 14 (the radial bore 92, gap 66) , and the lubricating oil is discharged to the outer peripheral side from both of the front end side discharge passage, which is provided on the distal end side of the chip 14 (the radial holes 94 and 96, the gap 98, the radial grooves 70), the internal thread by chip 14 made in breaking strength as lubrication oil is sufficiently supplied to the processing site thread forming of is further improved.