Carver Equipment, Hwy 301 South, Dunn, NC  28334
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Just a few notes that may help some folks.  Please visit us often at www.carvequipment.com for parts, service tips, equipment, information, toys, clothes or just to "hang out" and see what's new.

THREE POINT HITCH

The three point hitch is the farm and power equipment's mfg.'s industry standard for a hydraulically actuated mechanical linkage to attach, adjust, raise/lower and pull implements with powered transporters (tractors).

HISTORY
At first there were tractors. Then Implements. Each new manufacturer coming onto the market developed a different way of attaching (HITCHING) implements.  Through the early years of tractor development (1900s-1960s) a tractor purchaser had to purchase the same brand implements as the tractor to insure compatibility .  This caused a need for many complicated, unsafe and clumsy adapters to come on to the market. The many different type hitches causing all "short line without tractors" implement manufacturers grave concerns in marketing and design.

TRACTOR and IMPLEMENT manufactures agreed on one hitch system.  In the late 60s many of the "patent rights" of the first tractors expired allowing almost all the manufactures "world wide" to refine and improve and accept the THREE POINT HITCH as a standard. All did not.


The Three Point Hitch (sized Category) consist of:

A.  A POWERED HYDRAULIC SYSTEM
A powered hydraulic system with a raise/lower mechanical linkage that extends vertically between the two hydraulic arms and the two lower lift arms attached at a low point of the tractor. As the hydraulic arms are raised and lowered -- the implement lift arms with implement attached are as well.  The right hand vertical linkage that connects the RH hydraulic arm and the right hand implement lift (horizontal) arm is LENGTH ADJUSTABLE. This adjustment serves to "level" the Right and Left sides of the implement. It may be used to cause an implement to be "tilted." 

B. THREE ATTACHING POINTS
Two  of the three points are: 2 lift arms (right and left) that are raised and lower by the hydraulic system.  They attach to the tractor down and under the transmission / pto / final drive / hydraulic housings at  fixed positions near the lower outside edge of housings. 

C. HITCH LIFTING ARMS (Horizontal / 2 each/RH and LH)
One end is attached to the tractor, the other extends horizontally out behind the tractor approx. 10"/16" to serve as an attaching point for the implement. At the rear end of the lift arms is a hole. The hole is where a pin on the implement's three point hitch can be inserted and locked into position with a clip-pin.

D. CATEGORIES
The size of these holes and the length of these arms are enlarged as tractor horsepower increases. In general, the smallest holes - Category Zero (0) are found on little garden type tractors, Category One (I) 14/39 hp tractors, Category Two (II) 35/90 HP tractors, Category (III) and some other very heavy duty designed hitches are seen on "the big boys." They form the lower two (wide points) of a "A FRAME" looking triangle. The implement are usually attached to these two point with quick-clip pins.

STABILIZERS
The lower lift arms have ample swing flexibility so as to allow for easier attaching and alignment to the implement.  After the implement is attached, the pins and secured, the operator has to make sure that the implements and hitch do not swing into the inside rear walls and tread of the tires. This is accomplished by adjusting the stabilizers on each lift arms. Stabilizers may be chains, turnbuckle or telescoping linkage.

TOP LINK
The third part of the  three  points is the top link, sometimes called the center link, adjusting link, top arm -- etc.  It is "the pivoting point" of the linkage and is "most used point" for making important FRONT and REAR implement adjustments.
     The turnbuckle housing with females thread inside. One end is threaded with  RH threads, the other has left hand threads.  It is the point at the top of the "triangle A frame." The link is a telescopic threaded (RH Threads on one end - LH Threads on the other) turnbuckle. Twisting the center turnbuckle housing) clockwise you lengthen the link.  This causes the rear on a mounted implement to be lowered / the front raised and counterclockwise motion the opposite effect.  Hence serving a major factor in the implements performance and productivity.  Operators who master this adjustment "fine tuning" are well on their way to "becoming a skilled operator."  Three point hitches are most often found on the rear of tractors. They may also be added to the front of tractors, on skid steer loaders and any other vehicle or transporter.

Good luck to you in the three point operation. Remember, there is still as much to learn about it as we've discussed here. The draft control for farming tractors, telescopic lift arms, quick coupling hitches, remote hydraulic features, top and tilt features and many more areas of consideration may be pursued.

Just remember to never stand in between the tractor and the implement that you are connecting or disconnecting. Stay in focus and "think safety." 

Thanks, 
Steve
Steve Carver
Carver Equip.
Dunn NC