Theoretical analysis on chatter vibration in drilling and its suppression

The stability chart of chatter vibration occurring in drills for deep hole machining was investigated theoretically. Furthermore, suppression of the chatter vibration was attempted by using various drills with different point configurations and an impact damper. From these investigations, the following facts were clarified. Not only unstable regions but also an envelope line coming into contact with them is an important index for the occurrence of chatter vibration. When there is no vibration-inhibiting effect of the drill flank surface, the critical value λ2ect of the effective logarithmic decrement indicated by the envelope line is an important specific value in relation to the occurrence of chatter vibration. The smaller is the factor related to the cutting resistance, the greater is the factor related to the vibration-inhibiting effect on the drill flank surface; or the smaller is the factor relating to the soft spring characteristic, the less likely it is for chatter vibration to occur. It is very difficult to suppress the chatter vibration by changing the drill point configuration. If the logarithmic decrement of the drills becomes greater than the above mentioned λ2ect by the application of an impact damper, the chatter vibration can be suppressed completely.