These are the style of nut I was referring to. They eliminate a need for a lock washer or flat washer on the nut side. The ribs bite into the metal to lock them in place. As a bonus, they are easier to remove because they hold themselves until the bolt is loosened. The bolt itself has to be backed out once tight, you will not be able to turn the nut so never use them on a stud/nut combination.
I use them on everything I have to supply or change out the hardware for. They will be on my tooth bar when I reinstall it in the spring. If they are good enough for 150ton rated cranes, they are good enough for a little tractor.