Hitch Pin
The cylindrical pin that connects the implement to the lower link or top link socket and carries shear force. Its diameter varies with the three-point linkage category: on the lower link 17 mm for Cat.0, 22.4 mm for Cat.1, 28.7 mm for Cat.2 and 37.4 mm for Cat.3. Once the pin is seated it must always be locked with a safety clip or split pin.
The hitch pin carries the draft force as a shear load and is the single most critical part of the linkage. Using a pin smaller than the category leaves play in the socket; this play both creates impact loading and, by making the pin oval, leads to breakage over time.
- If there is noticeable oval wear, a notch or bending on the pin, the pin is replaced; it is not built up by welding.
- Never take an implement on the road without the safety clip fitted.
- Do not put your finger in the pin hole while attaching the implement; use a bar or a quick-hitch coupler for alignment.
What makes attaching and detaching implements easier is not the pin itself but being able to align the lower links with the pins to the millimetre. A fender switch, or being able to control an electronic retrofit kit from outside the cab, is exactly what helps here: standing beside the implement, you raise and lower the linkage with short taps and align the pin single-handed.
Context in which this term is used: Converting a tractor hydraulic lever to electronic control