Tractor 3 point hitch - size categories, components

A three-point hitch is a widely used type of hitch for attaching plows and other implements to an agricultural or industrial tractor. Three points resemble either a triangle or the letter A. Three-point attachment is the simplest and reliably static connection of plows and other agricultural machinery.

Attachment components

A three-point hitch consists of several components that work together. These include the tractor's hydraulic system, attachment points, lifting arms and stabilizers.

Three-point hitch systems consist of three movable levers. The two lower levers (links) - the lifting links of the coupling device - are controlled by the hydraulic system and provide lifting, lowering and even tilting of the levers.

The upper center arm, called the top linkage, is movable but not normally actuated by the tractor's hydraulic system.

Each hinged component has holes for fastening tools or quick-disconnect hooks into which the apples of the hinge are inserted.

The lifting levers of the attached (hitch) device are actuated by the tractor's own hydraulic system. In modern three-point hitch systems, there is often a traction adjustment mechanism. Attachment thrust, the amount of force required to pull the attachment, is determined by the top linkage, and the hydraulic system automatically raises the levers slightly when traction increases and lowers the levers when traction decreases.

Size categories:

There are five different hitch sizes, called categories (Cat). Higher-end hitches have stronger lifting arms and larger connecting pins

Cat.	Tractor Power	Top Link Pin Diameter	Lifting Arm Pin Diameter	Lower hitch spacing
0	up to 20 hp (15 kW)	16 mm	16 mm	510 mm
1	from 20 to 45 hp (from 15 to 34 kW)	19 mm	22 mm	710 mm
2	from 40 to 100 hp (from 30 to 75 kW)	25 mm	29 mm	860 mm
3	from 80 to 225 hp (60 to 168 kW)	32 mm	37 mm	1000 mm
4	over 180 hp (134 kW)	44 mm	51 mm	1200 mm

There are also variants of the above categories labeled N (narrow). They use the pin sizes of the indicated category but the width of the category one step below. N variants are common for "quick hitch devices" and allow larger tractors to easily connect to smaller utility implements.

Tractor Linkage Details:

Lower Link Hooks