In the process of turning large pitch thread

the contact relationship between tool and workpiece are constantly changing due to vibration caused by machine

cutting tool and workpiece

so that the cutting process is unstable. The existing vibration test methods can not reveal the composition and the influence degree of turning vi- bration when turning large pitch thread. The vibration characteristics of turning large pitch thread is researched by using the dynamic model of workpiece tow freedom and the cutting tool three degrees of freedom

vibration response testing and identification methods are put forward

incentive criterion of vibration is established

and six kinds of vibration time domain and frequency domain feature parameters are extract. The response characteristics of the machine tool spindle to the tool rotating speed

the radial cutting depth and the machining allowance are revealed. Resuits showed that the excitation caused by machine tool spindle idling vibration and cutting force high frequency vibration of tool determine the turning large pitch thread cutting vibration behavior.