This International Harvester (IH) promotional film describes the five basic functions performed by the modern self-propelled combine: 1) Cutting: All of the crop must enter the machine. 2) Feeding: The crop must be delivered to the cylinder. 3) Threshing: Performed by the cylinder (the threshing drum) operating against the concave (the inside surface of a slotted half-drum lying next to the cylinder). 4) Separating: The grain must be separated from rest of the plant by such mechanisms as straw-walkers. 5) Cleaning: the grain must be cleaned of chaff and other debris by the chaffer, sieves, and blower fan. On very steep slopes such as those in the Palouse region of the northwestern United States, self-leveling combines must be used.
—yortsnave