But why is this better than rotating the screw?,(reply>), Less dust. Turning the screw forces air upwards, which can blow the dust more than the pure lifting motion of the cylinder.,(reply>), @Ragnhild Well they said that in the video, yes, but why would there be any difference on that score if the screw is rotated relative to the housing or the housing is rotated relative to the screw?,(reply>), I suspect it's because there's less risk of crushing the material being lifted.