Do Damped Toolholders work?

Categories: Milling Tips

Let's explain why damping (that is the correct term, "dampening" means to make wet) works for boring bars and not so much for milling toolholders. The green and red charts represent the different toolholder responses to being hit with a hammer one time with the same force. They both deflect, rebound and continue to vibrate until they return to rest. The tool on the left clearly stops vibrating sooner than the tool on the right. Almost half the time, so it's better, right? Not so fast. Milling tools do not hit the workpiece one time and wait for it to stop vibrating. The chart at the bottom shows that at 10,000 RPM the cutter's teeth are impacting the workpiece at intervals of 0.8 to 3 milliseconds depending on the number of teeth the cutter has. Now, look at the dotted lines we added to the red and green graphs. Both toolholders deflect the same amount in first 25 milliseconds. But we will never get there, the next teeth has already made impact and started the process over again, as many of 30 times over! We are certainly never getting to the full damped state at 350 milliseconds.

In boring, the damped bars work because the cutting edge never leaves the workplace, so the faster absorption of the vibration has a chance to make a difference.

Damped tools do not ELIMINATE vibration, they only lower its frequency. They can still chatter if the frequency is not in harmony with the tooth impacts