It would have been used to separate grain from the broken straw, whole or broken ears, chaff and weed seeds after threshing using flails, long before the invention of combines or even threshing machines. They invariably have handles at both ends to enable two men to move the machine around the barn as required.

It is operated by the handle at the side of the machine, this being geared to turn a large wooden 'fan' to produce a strong current of air. The partially cleaned grain from the Aspirator feeds from a storage bin into the hopper on the top of the winnower before flowing through the machine at a controlled rate. As it falls through the air current, chaff and other light material are blown from the rear of the machine, and the grain drops onto a series of wire sieves. These are shaken as the handle is turned, the first two removing larger items, such as unthreshed wheat ears, pieces of straw, or poppy heads, but allow the grain through. The third, with a smaller mesh, removes any small grain or weed seeds but retains the larger grain. The cleaned grain is then discharged from hatches on the sides of the machine before being transferred to either the Millstones for milling or to the Combined Milling Machine for kibbling for animal feed.

Although almost all wheat grain is now harvested by combines that include grain cleaning, the Aspirator and Winnower are kept to demonstrate earlier methods of grain cleaning.