The Category I  three -point hitch is based on three mounting points for the implement. The lift arms are the 2 steel or cast arms that extend rearward and provide the lift and are the pull-point for the implement.  The top link is the third mounting point and extends from a top middle position out the rear of the tractor. Comparatively very little rearward force is applied from the top link unless the implement becomes bound up or twisted in some way. The standards require that the pin sizes on the implement and corresponding lift-arm holes be 7/8" (.88-.89). The top link uses a 3/4" (.76-.77) pin and hole.  The distance from the tail of the PTO shaft to the lift arm ends is approximately 14 inches. The minimum spread between the lower lift arms will be about 26-27 inches, the maximum spread is normally out to 33 inches or more.

Some implements are designed to run at between 750 and 1000 RPM.  Although other minor variations are in use around the world, the standard shaft for 1000 RPM is a 1 and 3/8 inch - Twenty One spline.

The 540 RPM connection will use a 1 and 3/8 - six spline shaft.  Since 1000 RPM produces only approximately 1/2 the torque of a 540, smaller HP tractors rely heavily on this slower speed for increased torque.  All of our Jinma Farm Boss tractors come with the 540 - six spline shaft and almost every small PTO driven implement in your yard or on the market will fit.  A word of caution - never attempt to run your 540 equipment at 1000 RPM.

(1) Wrap up over 6 feet of shoe lace per second. How long is your shoe lace?
(2) Wrap your arm or leg around the PTO shaft nine times in a second? How flexable are you?
(3) Produce second degree burns on your skin when caused by synthetic cloth movement at high speeds.
(4) A very strong man can generate about three-fourths of one horsepower. What is your tractor HP?