For oil or for milk, the spinner part would look similar to this. Only in this case the gears and crank are on top, rather than on the bottom. I recently saw one in an antique shop with glass bottles, gear case on the bottom, in cast iron, with many brass parts. I don't think it needed clamping down, weighed over 50 lbs. The disconnect on the handle, the push in part that allows free wheeling, would allow the spinning bottles to slowly come to a halt, so as to not disturb the separated fluids.