page_title: Threshing machine
section_title: In Europe and Americas
hierarchical_section_title: Threshing machine / Modern developments / In Europe and Americas
caption_attribution_description: English: Threshing of paddy by machine, Bangladesh বাংলা: কলের সাহায্যে ধান মাড়াই, বাংলাদেশ
context_page_description: A threshing machine or a thresher is a piece of farm equipment that threshes grain, that is, it removes the seeds from the stalks and husks. It does so by beating the plant to make the seeds fall out.
  Before such machines were developed, threshing was done by hand with flails: such hand threshing was very laborious and time-consuming, taking about one-quarter of agricultural labour by the 18th century. Mechanization of this process removed a substantial amount of drudgery from farm labour. The first threshing machine was invented circa 1786 by the Scottish engineer Andrew Meikle, and the subsequent adoption of such machines was one of the earlier examples of the mechanization of agriculture. During the 19th century, threshers and mechanical reapers and reaper-binders gradually became widespread and made grain production much less laborious.
  Michael Stirling is said to have invented a rotary threshing machine in 1758 which for forty years was used to process all the corn on his farm at Gateside. No published works have yet been found but his son William made a sworn statement to his minister to this fact. He also gave him the details of his father's death in 1796.
context_section_description: Modern day combine harvesters (or simply combines) operate on the same principles and use the same components as the original threshing machines built in the 19th century.  Combines also perform the reaping operation at the same time.  The name combine is derived from the fact that the two steps are combined in a single machine.  Also, most modern combines are self-powered (usually by a diesel engine) and self-propelled, although tractor powered, pull type combines models were offered by John Deere and Case International into the 1990s.
  Today, as in the 19th century, the threshing begins with a cylinder and concave.  The cylinder has sharp serrated bars, and rotates at high speed (about 500 RPM), so that the bars beat against the entire plant as it is mechanically fed from the reaping equipment at the front of the combine to the gap between the concave and the rotating beater/cylinder.  The concave is curved to match the curve of the cylinder, and the grain, now separated from the plant stalks falls immediately through grated openings in the concave as it is beaten.  The motion of the rotating cylinder thrusts the remaining straw and chaff toward the rear of the machine.
  Whilst the majority of the grain falls through the concave, the straw is carried by a set of "walkers" to the rear of the machine, allowing any grain and chaff still in the straw to fall below.  Below the straw walkers, a fan blows a stream of air across the grain, removing dust and small bits of crushed plant material out of the back of the combine. The residues fall to the ground and occasional are collected for other purposes, such as fodder.
  The grain, either coming through the concave or the walkers, meets a set of sieves mounted on an assembly called a shoe, which is shaken mechanically.  The top sieve has larger openings, and serves to remove large pieces of chaff from the grain.  The lower sieve separates clean grain, which falls through, from incompletely threshed pieces.  The incompletely threshed grain is returned to the cylinder by means of a system of conveyors, where the process repeats.
  Some threshing machines were equipped with a bagger, which invariably held two bags, one being filled, and the other being replaced with an empty.  A worker called a sewer removed and replaced the bags, and sewed full bags shut with a needle and thread.  Other threshing machines would discharge grain from a conveyor, for bagging by hand.  Combines are equipped with a grain tank, which accumulates grain for deposit in a truck or wagon.
  A large amount of chaff and straw would accumulate around a threshing machine, and several innovations, such as the air chaffer, were developed to deal with this.  Combines generally chop and disperse straw as they move through the field, though the chopping is disabled when the straw is to be baled, and chaff collectors are sometimes used to prevent the dispersal of weed seed throughout a field.
  The corn sheller was almost identical in design, with slight modifications to deal with the larger kernel size and presence of cobs.  Modern-day combines can be adjusted to work with any grain crop, and many unusual seed crops.
  Both the older and modern machines require a good deal of effort to operate. The concave clearance, cylinder speed, fan velocity, sieve sizes, and feeding rate must be adjusted for crop conditions.
caption: Threshing of paddy by machine, Bangladesh.
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