It is difficulty to solve the problem of gracile shaft when the ratio is more than 25 that shaft’s length divide by diameter,by using reverse cutting,clamp &withstand device and mushroom head pin to add rigidity and decrease transfiguration of flexible cutter pole,successfully machining long lead screw when the ratio is 54 that it’s length divide by diameter,then achieve the demand on the drawing.

The paper uses process capability indices for tool wear processes,from which the tool replacement time that meets the needs of customers for minimum process capability indices is obtained.