I have just about finished building one and need to know about the action it should have. I read on a web site for commercial polishers that they use 3600 rpm as the speed, so I set it for that. But I don't know how vigorous it should be. Does one of these *just* vibrate, or is there a noticeable shaking to the action? Putting it quantitatively, how much displacement (side to side) does a v-p have?