The vibration amplitude curve is shown in the following figure. There is no vibration at node, but the largest stress appears at these points.

The machining efficiency is determined by the following factors,

1) Vibrational amplitude of the tool

2) Working pressure to the work piece

3) Condition of abrasive fed to the work piece

Too large working pressure a well as too small pressure results in poor machining efficiency. The abrasive is absolutely necessary. Too little or too much will result in poor efficiency. If no abrasive is present at the end of the tool, machining is almost impossible and the work piece may be broken. Especially in case of deep drilling, it is necessary to move the work piece up and down along the tool, once in a while, to allow the abrasive to reach the drilling tool end.