To improve the treatment efficiency of aluminium alloy aperture, getting adopted on the design that cuts craft increase mental allowance and the measure that raise feed rate, the result is brought about cut bits to become already thick grow again. This kind thick long model cut bits to twine bring about cutting tool possibly on broach to break off; In addition, cut bits " bite " the exterior surface roughness that can damage aperture into workpiece surface and dimension precision; And these blemish take below one working procedure to will be caused stop machine nap to reach increase addition trouble. Cut treatment to maintain large surplus, fast feed to get, eliminate at the same time thick grow the malady that cuts bits to bring, the company developed Japan to have bit of PCD of the function that break bits 2 times. Through will plunging pointed cutting knife the design becomes the figure that can break bits 2 times, can make generate cut bits finely change, solve the problem of the control that cut bits of treatment of aluminium alloy aperture effectively thereby.