Linkage, Jacks, & Hardware The Three-Point Hitch System
Top Link Pin Top Link Clevis Lift Arm Stabilizer Arms Lynch Pins Drawbars
Introduction A typical tractor three-point hitch system is standard on almost all farm tractors today. The basic function of the system is the attachment and adjustment of agricultural implements. The three primary parts of the system are the top link and two lower lift arms as shown in gold and brown in the illustration above. Special pins are used to fasten the implement at these three points: top link pins and draw pins (lift arm pins). Adjustment of one or all of these components allows the tractor operator to raise, lower or tilt an implement. The three-point linkage parts described in this catalog are built to standard specifica- tions set by the American Society of Argicultural Engineers (ASAE) described in the table on the right.
Category 1, 2, 3 and 4 Categories are used to classify tractors by drawbar horse- power. The table below gives the dimensions and the horsepower ratings that are associated with these three categories.
Maximum Drawbar Horsepower
Cat. 0 - up to 20 Cat. 1- up to 45 Cat. 2- 40 to 100 Cat. 3- 80 to 225
Top Link Pin Dia.
5/8" 3/4" 1"
1–1/4" Cat. 4- 135 to 300 1–3/4"
Pull/Draw Pin Dia.
1–1/8" 1–7/16" 2"
Stanard Lift Arm Spacing
20" 26" 32" 38" 46"
Top Link Connection Top link pins are always unthreaded and are held in place by either a lynch pin, or in some cases, a large “R” clip pin. See below. Top links and top link pins vary in length, but their respective ball socket holes and pin diameters are standardized by horsepower category.
LG 766 Linkage, Jacks, & Hardware Top Link Connection
Lift Arm Connection Most lift arm pins are threaded on the end that bolts to the implement bracket. The unthreaded end with the cross hole accommodates the ball socket of the lift arm. The lift arm is secured on the pin with a lynch pin or large “R” clip pin. See below. Lift arms and lift arm pins vary in length, but their respective ball socket holes and pin diameters are standardized by horsepower category.