A threshing machine is a device that separates grain seeds from the rest of the harvested plant. When farmers cut down wheat, oats, or other grain crops, they get tall stalks with the valuable seeds still attached. Threshing machines shake, beat, or rub these stalks to knock the seeds loose, then blow away the unwanted chaff (the dry, papery husks) and straw, leaving clean grain behind.

For thousands of years, farmers did this backbreaking work by hand, beating grain with sticks called flails or having animals walk over it. The invention of mechanical threshing machines in the late 1700s transformed farming. What once took days of exhausting labor could suddenly be done in hours. By the 1800s, large steam-powered threshing machines traveled from farm to farm, with neighbors gathering to help feed stalks into the roaring machine as it thundered through the harvest.

Modern farmers use combine harvesters, which cut and thresh grain in one operation, but the basic idea remains: separate the precious seeds from everything else.