Handpieces similar to the Giromatic neither rotate nor linearly oscillate.
They simply rotate a few degrees
(generally about 45) and then rotate back.
So the cutting cannot be by rotation.
Since the handpiece itself does not seem to cut and yet dentists in Europe and America have used these handpieces for years the question is, "How do they work?"
When standards testers are measuring friction they take a flat surface made usually of steel and a block of the same material which has a broad flat surface and put the lubricant between them.
Then they elevate one corner of the plate until the block begins to slide, noting the angle at which the sliding began.
But they do not use that measurement.
They lower the corner, decreasing the angle of the plate until the sliding stops.
This then determines the effectiveness of the friction reducing capabilities of the lubricant.
The reason for this seemingly strange practice is that a body in motion has a lower co-efficient of friction than a body at rest.
An example might be, trying to push a large heavy box across the floor.
Once you get it going, you want to keep it going because it takes less energy to keep it moving than to start it again.
When a file is moving it has a lower coefficient of friction against dentin than when it is stopped.
The rotational oscillation simply lowers the coefficient of friction of file against dentin and makes the cutting smoother.
Thus YOU must do the up and down linear oscillation to get the file to cut. Simply holding it in place does very little good.
The minimum amplitude of this linear motion is one interflute distance. That is the file must be moved enough that the spot occupied by one flute is not occupied by the flute below it.
Any more and you risk breakage. Any less and it will not cut.