The way I understand it is that with the smaller diameter pad on a DA there is less surface area and weight of the pad and so it will actually cut more than the same type of pad in a bigger diameter at the same machine speed. This is why you can turn the speed down a bit in comparison.
On a rotary, when you increase the pad diameter, the outer edge has to travel further with each revolution, and thus it has to spin faster, creating more cut.
This is absolutely correct !
I know it has been debated on and on, but I am absolutely positive that the outer edge of a spinning disk will always be going faster than the center of that spinning disk..
Here is a more graphic example -
On the older Snapper lawnmowers - the ones that had a spinning disk driven by a belt that was connected to the engine, there was a rubber disk that was mounted vertically on top of that spinning disk, that was controlled by a lever at the end of the handle.
The rubber disk was connected to the rear wheels through a differential that just drove them together - like rear wheel drive -
When you moved that rubber disk across the spinning disk, that engaged the mower wheels, the mower took off..
When you moved that rubber disk to the EDGE of the spinning disk underneath, the mower speed was the Fastest....
When you moved that rubber disk to the Center of the spinning disk underneath, the mower speed was the slowest...
The speed you need and pressure you apply to that particular scratch, combined with the pad type and compound/polish used will never be just "this speed and pressure", because there are too many other variables to add to the equation..
But as has already been stated above, the smaller diameter pad will be spinning faster than a much bigger pad at the Center because of the small diameter...
Good Luck !
Dan F
