Threshing

threshing or thrashing, separation of grain from the stalk on which it grows and from the chaff or pod that covers it. The first known method was by striking the reaped ears of grain with a flail. In another early method horses or oxen trod out the grain from stalks spread on a threshing floor. In both cases the straw was raked away and then the mixture of grain and chaff was winnowed, i.e., tossed into or poured through a current of air so that the light chaff was blown away from the heavier grain. In 1784 a Scotsman, Andrew Meikle, devised a threshing machine. Sheaves of grain were fed into a revolving cylinder armed with wooden beaters. Another toothed drum raked away the loose straw and pushed the remaining chaff and grain through a sieve onto a series of rollers that further separated the chaff from the grain in preparation for winnowing. The principle of Meikle's machine has been retained in all threshing machines up to and including the modern self-propelled combines.

Bibliography

See M. Partridge, Farm Tools through the Ages (1973).

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Threshing 

separation of the seeds (or fruits) from the ears, tassels, heads, and cobs of plants. It is one of the basic operations in harvesting grain and other agricultural crops. It is performed by combines and threshers in the field and at the threshing floor and is usually combined with cleaning and grading of seeds (grain). The quality of threshing work is evaluated by the degree of completeness and the number of broken seeds and seeds that remain in the straw and chaff.