CAD View of Milling

​The first image is the CAD/CAM view of a milling cutter. A perfect cylinder, 100% rigid, no imbalance, no runout and NO TEETH, therefore no deflection or vibration. Unfortunately, it doesn't work quite like that. The second image shows the effect of one tooth impact. the tool deflects, rebounds and then returns to the centerline. That is one cycle, expressed as Hertz (Hz), of vibration. The number of cycles per second, or Hz, is the tool point's frequency. The third image shows the results of the tool point's flexibility. Teeth can arrive at the workpiece too early, too late or on-time. The spindle speed has to be tuned to the tool's back and forth frequency to get the timing of these tooth impacts just right.