Chuck jaw grinding blocks

After many years of use, the jaws on a 3 jaw chuck can get worn. If, like in my case, they go bellmouthed, a rod in the chuck can still wobble around.
I made three possible devices to preload the jaws. They all work by engaging the tapered end of the jaws where they are parallel to the other jaws. Each device can be trapped in this area and clamped down on. This loads the scroll just like the jaws are on a real part, allowing you to grind the jaw tips concentric and straight.
I like the three legged one the best; that's what I actually used on my chuck. The three block style is OK, but fiddly to install. The plasma cut plate part should also work quite well, but I didn't actually make it.
I've got youtube videos of using the three leg style on my chuck and of testing it afterwards.