@Robert M posted:
I haven’t used a tow bar in 30 years, and I don’t remember the OD of the pins, but they are not flimsy. There is very little load on those pins. They might even be off the shelf 5/8” hitch pins.
For perspective, a trailer hitch drawbar uses one 5/8” hitch pin, no matter the size of the hitch, from class 1 all the way to class V, which is greater than 10,000lbs.