Three-point hitch

Last updated
Ursus C-360 tractor and mowing deck, attached by a three-point linkage and driven by a PTO shaft Ursus C360 PICT0076.jpg
Ursus C-360 tractor and mowing deck, attached by a three-point linkage and driven by a PTO shaft

The three-point hitch (British English: three-point linkage) is a widely used type of hitch for attaching ploughs and other implements to an agricultural or industrial tractor. [1] [2] The three points resemble either a triangle, or the letter A. Three-point attachment is the simplest and the only statically determinate way of joining two bodies in engineering.


A three-point hitch attaches the implement to the tractor so that the orientation of the implement is fixed with respect to the tractor and the arm position of the hitch. The tractor carries some or all of the weight of the implement. The other main mechanism for attaching a load is through a drawbar, a single point, pivoting attachment where the implement or trailer is not in a fixed position with respect to the tractor.

The primary benefit of the three-point hitch system is to transfer the weight and resistance of an implement to the drive wheels of the tractor. This gives the tractor more usable traction than it would otherwise have, given the same power, weight, and fuel consumption. For example, when the Ford 9N introduced Harry Ferguson's three-point hitch design to American production-model tractors in 1939, it was a light and affordable tractor competing principally with row-crop tractors such as Farmalls that did not yet have three-point hitches. At 2,500 pounds (1,100 kg), the 9N could plow more than 12 acres (5 hectares) in a normal day pulling two 14-inch (360 mm) plows, [3] outperforming the tractive performance of the heavier and more expensive Farmall F-30 model. [3] The hitch's utility and simplicity have since made it an industry standard.


Three-point linkage on a Ferguson 35 tractor.
The tractor and linkage are painted gold. The grey bars are a separate implement (a towing ball hitch) attached to the linkage. Three-point linkage and tow hitch implement, Ferguson TEF, Abergavenny.jpg
Three-point linkage on a Ferguson 35 tractor.
The tractor and linkage are painted gold. The grey bars are a separate implement (a towing ball hitch) attached to the linkage.

The three-point hitch is made up of several components working together. These include the tractor's hydraulic system, attaching points, the lifting arms, and stabilizers.

Three-point hitches are composed of three movable arms. The two lower arms—the hitch lifting arms—are controlled by the hydraulic system, and provide lifting, lowering, and even tilting to the arms. The upper center arm—called the top link—is movable, but is usually not powered by the tractor's hydraulic system. Each arm has an attachment device to connect implements to the hitch.

Each hitch has attachment holes for attaching implements, and the implement has posts that fit through the holes. The implement is secured by placing a pin on the ends of the posts.

The hitch lifting arms are powered by the tractor's own hydraulic system. The hydraulic system is controlled by the operator, and usually a variety of settings are available. A draft control mechanism is often present in modern three-point hitch systems. The draft of the implement, the amount of force it is taking to pull the implement, is sensed on the top link and the hydraulic system automatically raises the arms slightly when the draft increases and lowers the arms when the draft decreases.

Size categories

Adjustable three-point ball on lift arm. Ball may be rotated to fit either Category I or II implements Cat I and II ball closeup.jpg
Adjustable three-point ball on lift arm. Ball may be rotated to fit either Category I or II implements
Rear three-point hitch of a Case IH tractor with implement attached by the drawbar Heckhubwerk mit Fanghaken Cat3, Case IH Puma 225 CVX.jpg
Rear three-point hitch of a Case IH tractor with implement attached by the drawbar

There are five different hitch sizes, called categories. The higher category hitches have sturdier lift arms and larger connector pins. [2]

CategoryTractor powerTop link pin diameter*Lift arm pin diameterLower hitch spacing
0Up to 20 hp (15 kW)58 in (16 mm)58 in (16 mm)20 in (510 mm)
120 to 45 hp (15 to 34 kW)34 in (19 mm)78 in (22 mm)28 in (710 mm)
240 to 100 hp (30 to 75 kW)1 in (25 mm)1 18 in (29 mm)34 in (860 mm)
380 to 225 hp (60 to 168 kW)1 14 in (32 mm)1 716 in (37 mm)40 in (1,000 mm)
4More than 180 hp (130 kW)1 34 in (44 mm)2 in (51 mm)48 in (1,200 mm)

There are also variants to the above categories denoted by N, (narrow). These utilize the pin sizes of the listed category, but the width of a category one step lower. The N variations are common in "quick hitches" and allow larger tractors to easily hook onto smaller utility implements.

* refers to implement end; tractor end not specified


Before the 1940s, most hitching of farm implements to tractors was done simply with a drawbar, on the same principle as a modern tow hitch. The drawbar was a flat bar with holes in it, and the implements were trailers, with tongues that attached to the drawbar with a pin through a hole. The main reason why this was the default hitching idea is that it was the natural follow-on from the days of horse-drawn implements, which were towed as trailers by the horse or team (and often had an operator's seat). In fact, for decades during the mechanisation of agriculture in Europe and North America, as tractors gradually replaced horses in increasing degrees, existing implements from the horse era were often what the tractor pulled. Towing with a drawbar is a good, practical system for many purposes, and it has continued to be used even up to today, but the three-point hitch outperforms it in several ways (described below).

Harry Ferguson patented the three-point linkage for agricultural tractors in Britain in 1926. He had long been a champion of the importance of rigid attachment of the plough to the tractor. The idea did not originate with him, but he led its popularization over many years of development, explaining, and selling. During the decade of 1916 to 1926 he developed his ideas through various iterations, duplex and triplex, mechanical and hydraulic, to arrive at the patented form. During the next decade, he continued explaining and selling his hitches and implements and even produced his own model of tractor in cooperation with David Brown Ltd. via the Ferguson-Brown Company. The particular geometry of the linkage that attached the plough to the tractor enabled forces generated by the plough to be applied to the rear wheels of the tractor. This redirected the plough's resistance into downward force on the drive wheels, which enabled Ferguson's tractor to be much lighter and more manoeuvrable than earlier models of farm tractor with equivalent tractive force and traction. As a result his tractor could operate on soft ground and caused less compacting damage to the soil in comparison with other tractors of the time, and it could produce given amounts of work with less time and fuel. The hydraulically operated and controlled three-point hitch used the draft of the mounted tool to moderate the depth of the tool and therefore the load on the tractor (automatic depth control or draft control). In addition, the three-point hitch would prevent the tractor from flipping backwards on the drive wheels if the implement being dragged were to hit a rock or other immovable obstruction. Ferguson and his colleagues developed several innovations to this device (e.g., the hydraulic lift and depth control) which made the system workable, effective, and desirable. In 1938, after almost two decades of trying to sell Henry Ford on using Ferguson's system on tractors mass-produced by Ford, Ferguson finally convinced Ford. The American mass-market debut was via the Ford-Ferguson 9N in 1939.

The Ferguson system, as it was called, was not just an improved hitch but rather the hitch plus an entire line of implements purpose-built to make full use of its advantages. During the 1940s, it was so advantageous and popular that other manufacturers were compelled to come up with competing hitch improvements that could also be pitched as proprietary "systems" with at least some of the features of the Ferguson system (such as quick, easy hitching and unhitching, implement raising and lowering controlled from the tractor seat, and treating the tractor and implement as a unit rather than an articulated pair). Thus, International Harvester developed its Fast Hitch and began to advertise the notion of "farming with the Farmall system" and Allis-Chalmers introduced its Snap-Coupler which allowed the operator to hook and unhook implements without leaving the operator's seat. Likewise, JI Case developed its Eagle Hitch, and similar path was followed at John Deere. Some of these systems, with one-point or two-point hitching, were not well suited to lifting heavy implements. They also presented the problem of incompatibility between brands of tractors and implements, applying pressure toward vendor lock-in that many farmers resented. During the 1950s and 1960s, farmers often would have to purchase the same brand implements as their tractor to be able to hook up the implement correctly or to best effect. If a farmer needed to use a different brand of implement, an adaptation kit—which were typically clumsy, ill-fitting, or unsafe—was sometimes needed. The pressure toward vendor lock-in was a two-edged blade for the salespeople. It was an advantage in cases where it encouraged the sale of implements (e.g., a farmer decided to purchase not just a tractor but also new implements to replace his old ones, betting on increased productivity to make it worth the cost), but it was a disadvantage to the extent that farmers didn't see the value in a special new hitch if they couldn't afford also to buy new implements to make full use of it or felt uneasy about buying new implements when they already had existing implements that were still usable. Ferguson often faced the latter problem in the UK and Ireland in the 1920s and 1930s, and it also applied to the competitors' proprietary hitches of the 1940s and 1950s.

In the 1960s, as patents on the technology expired, tractor and implement manufacturers agreed on the three-point hitch as the one standard, interchangeable, full-featured system to hitch implements to tractors. With the advent of nonproprietary status, the manufacturers were able to refine the system and create useful modifications. Now, nearly all manufacturers have adopted some standardised [1] form of the modern three-point hitch system; many companies also offer safe adaptation kits for converting the non-standard hitch systems to the three-point hitch system.

See also


  1. 1 2 ISO 730:2009, Agricultural wheeled tractors -- Rear-mounted three-point linkage -- Categories 1N, 1, 2N, 2, 3N, 3, 4N and 4, ISO, retrieved 2015-08-15
  2. 1 2 Three-Point Hitch,, retrieved 3 November 2013
  3. 1 2 Pripps & Morland 1993 , p. 60.


Related Research Articles

Plough Tool or farm implement

A plough or plow is a farm tool for loosening or turning the soil before sowing seed or planting. Ploughs were traditionally drawn by oxen and horses, but in modern farms are drawn by tractors. A plough may have a wooden, iron or steel frame, with a blade attached to cut and loosen the soil. It has been fundamental to farming for most of history. The earliest ploughs had no wheels, such a plough being known to the Romans as an aratrum. Celtic peoples first came to use wheeled ploughs in the Roman era.

Tractor Engineering vehicle specifically designed to deliver a high tractive effort

A tractor is an engineering vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture or construction. Most commonly, the term is used to describe a farm vehicle that provides the power and traction to mechanize agricultural tasks, especially tillage, but nowadays a great variety of tasks. Agricultural implements may be towed behind or mounted on the tractor, and the tractor may also provide a source of power if the implement is mechanised.

Power take-off Methods for transmitting power from a source to an application

A power take-off or power takeoff (PTO) is any of several methods for taking power from a power source, such as a running engine, and transmitting it to an application such as an attached implement or separate machine.

Loader (equipment) Heavy equipment machine

A loader is a heavy equipment machine used in construction to move aside or load materials such as asphalt, demolition debris, dirt, snow, feed, gravel, logs, raw minerals, recycled material, rock, sand, woodchips, etc. into or onto another type of machinery. There are many types of loader, which, depending on design and application, are called by various names, including bucket loader, front loader, front-end loader, payloader, high lift, scoop, shovel, skip loader, wheel loader, or skid-steer.

Trailer (vehicle) vehicle that has a loading area but does not have its own drive

A trailer is an unpowered vehicle towed by a powered vehicle. It is commonly used for the transport of goods and materials.

Fordson former tractor brand

Fordson was a brand name of tractors and trucks. It was used on a range of mass-produced general-purpose tractors manufactured by Henry Ford & Son Inc from 1917 to 1920, by Ford Motor Company (U.S.) and Ford Motor Company Ltd (U.K.) from 1920 to 1928, and by Ford Motor Company Ltd (U.K.) from 1929 to 1964. The latter also later built trucks and vans under the Fordson brand.

Ferguson-Brown Company Defunct British agricultural machinery company

The Ferguson-Brown Company was a British agricultural machinery company formed by Harry Ferguson in partnership with David Brown.

Harry Ferguson Irish engineer and inventor

Henry George "Harry" Ferguson was an Irish-born British mechanic and inventor who is noted for his role in the development of the modern agricultural tractor and its three point linkage system, for being the first person in Ireland to build and fly his own aeroplane, and for developing the first four-wheel drive Formula One car, the Ferguson P99.

Caterpillar D6 Medium bulldozer

The Caterpillar D6 track-type tractor is a medium bulldozer manufactured by Caterpillar Inc. with a nominal operating weight of 18 tons. The military versions were classified as the SNL G152 medium tractor, under the G-numbers classification system used for army tractors.

Ferguson TE20

The Ferguson TE20 is an agricultural tractor designed by Harry Ferguson. By far his most successful design, it was manufactured from 1946 until 1956, and was commonly known as the Little Grey Fergie. It marked a major advance in tractor design, distinguished by light weight, small size, manoeuvrability and versatility. The TE20 popularised Harry Ferguson's invention of the hydraulic three-point hitch system around the world, and the system quickly became an international standard for tractors of all makes and sizes that has remained to this day. The tractor played a large part in introducing widespread mechanised agriculture. In many parts of the world the TE20 was the first tractor to be affordable to the average farmer and was small and light enough to replace the draft horse and manual labour. Many TE20s remain in regular use in farming and other work and the model is also a popular collector's item for enthusiasts today.

Cultivator farm implement used for secondary tillage

A cultivator is any of several types of farm implement used for secondary tillage. One sense of the name refers to frames with teeth that pierce the soil as they are dragged through it linearly. Another sense refers to machines that use rotary motion of disks or teeth to accomplish a similar result. The rotary tiller is a principal example.

Farmall Creation of the Farmall F12G tractor in 1937

Farmall was a model name and later a brand name for tractors manufactured by the American company International Harvester (IH). The Farmall name was usually presented as McCormick-Deering Farmall and later McCormick Farmall in the evolving brand architecture of IH.

Ford N-series tractor

The Ford N-series tractors were a line of farm tractors produced by Ford between 1939 and 1952, spanning the 9N, 2N, and 8N models.

Semi-trailer Trailer vehicle without a front axle

A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer, a tractor-trailer.


A subsoiler or flat lifter is a tractor-mounted farm implement used for deep tillage, loosening and breaking up soil at depths below the levels worked by moldboard ploughs, disc harrows, or rototillers. Most such tools will break up and turn over surface soil to a depth of 15–20 cm (5.9–7.9 in), whereas a subsoiler will break up and loosen soil to twice those depths.

Drawbar (haulage) One of the long bars between a pair of which an animal is harnessed to a carriage or other vehicle.

A drawbar is a solid coupling between a hauling vehicle and its hauled load. Drawbars are in common use with rail transport, road trailers, both large and small, industrial and recreational, and with agricultural equipment.

The Massey-Harris Model 101 was a tractor built by Massey-Harris from 1938-1946. Developed under the guidance of James S. Duncan, who gambled corporate losses would drop and won, the 101 introduced the Chrysler L-head inline six. The six would compete with Oliver's straight-six Model 70, while saving money on development of a whole new engine as well as taking advantage of Chrysler's existing parts and service network.

Allis-Chalmers ED40

The Allis-Chalmers ED 40 tractor was the last model made by the UK subsidiary of the American Allis-Chalmers Corporation before the plant at Essendine, Rutland, was closed in 1985. Introduced at the Smithfield Show, London in 1960, it retained all the features that rowcrop farmers required but in a manner that made it a universal farm tractor. Only diesel power was available from a four-cylinder ohv of 137.89 cu.ins. indirect injection engine made by the Standard Motor Co, Coventry. As the name may imply, the tractor had about 40 horsepower.

Porsche-Diesel 218 tractor model

The Porsche-Diesel Standard 218, also known as N 218, is the third generation of the two-cylinder Standard tractor series, manufactured by Porsche-Diesel Motorenbau GmbH in Friedrichshafen am Bodensee. The Standard 218 was produced in four different variations. It succeeded its predecessor, the Porsche-Diesel 208 in 1957. In total, the Porsche plant produced more than 12,000 Standard 218 tractors from 1957 to 1963.

Fortschritt ZT 300 series of 20 kN agricultural tractors

ZT 300 is a series of 20 kN agricultural tractors, produced from 1 September 1967 to 1984 by the VEB Traktorenwerk Schönebeck. It succeeded the RS14 Famulus series, and unlike the Famulus, the ZT 300 series was sold under the brand name Fortschritt. ZT 300 refers both to the initial ZT 300 model, and the ZT 300 series. In total, 72,382 units of the ZT 300 series were made. The model with the highest production figure was the ZT 303, which was introduced in 1972. It features an automatic all-wheel-drive system; in the early 1980s, it cost 81.000 Mark. Starting in 1983, the ZT 300 series was succeeded by the ZT 320.