Editing Threshing machine (section)

== Modern developments ==

===In Europe and Americas===
[[File:Agriculture of Bangladesh 10.jpg|thumb|Threshing of paddy by machine, Bangladesh.]]
Modern-day combines harvesters (or simply [[combine harvester|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, 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 occasionally 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.

===Another development in Asia===
[[File:Petrol powered threshing machine in Hainan - 01.ogv|thumbnail|Video of a petrol-powered machine threshing rice in [[Hainan]], China]]
From the early 20th century, petrol or diesel-powered threshing machines, designed especially to thresh [[rice]], the most important crop in Asia, have been developed along different lines to the modern combine.

Even after the combine was invented and became popular, a new compact-size thresher called a ''harvester'', with wheels, still remains in use and at present it is available from a Japanese agricultural manufacturer. The compact-size machine is very convenient to handle in small terrace fields in mountain areas where a large machine, such as a combine, is not usable.

People there use this harvester with a modern compact [[Reaper-binder|binder]].