Vibration-Control

Thin wall tubing is some of the most frustrating material to deep hole drill. The wall has almost no rigidity, so the cutting forces that would be negligible on a solid bar become critical. I have seen tubes collapse, chatter, ovalize, and ring like a bell when the drill contacts them. The key is understanding that you are not drilling a hole in a tube – you are drilling a hole through a structure that happens to be shaped like a tube. The structural integrity of the tube has to be maintained during the drilling process. ...

Why Thin Wall Cylinders Vibrate Thin wall cylinders vibrate during deep hole drilling because the wall flexes under cutting forces. The ratio of bore diameter to wall thickness determines how susceptible a cylinder is to vibration. In my experience, cylinders with a diameter-to-wall-thickness ratio above 10:1 will vibrate under normal cutting conditions. When the cylinder wall flexes, the cutting tool encounters an inconsistent depth of cut. The drill digs in deeper when the wall deflects away, then cuts less when the wall springs back. This alternating force creates chatter marks on the bore surface and can chip the cutting edges of the drill in extreme cases. ...