Reapers are machines designed to cut, or harvest, grain. As opposed to mowing machines, which are designed to cut green grass for hay, reapers are used in fields of mature grain whose stalks require a heavier serrated blade.

An early corn reaper built in southern Gaul during the first century a.d. consisted of a case with teeth mounted on a pair of wheels and pushed by an ox or donkey; Pliny the Elder (23-79 a.d.), the Roman naturalist, described it. However widespread its use might have been, reaper technology was lost over the centuries and was not retrieved until the early 1800s. Instead, sickles and shears were used for manual grain harvesting.

In 1805 Thomas Plucknett, an implement maker from London, England, patented a machine with a very sharp circular steel plate positioned parallel to the ground. The problem was that the grain...