Probably addressed due to a combination of stiffer grinding setup and a better job of individual preload on all the jaws. No way to tell for sure without disassembling the chuck and measuring/checking everything. Cracked jaws does not sound good, but would depend on how they were cracked. It would be good to hear what the final results actually were, not just that they were excellent.
Removing 3 jaws will grip smaller. That can work too. I used to do that now and again on the ones at work. Just remember to swap between sets every other time to even out wear. I.E. 1-3-5 this time, 2-4-6 next time.
After this round of grinding, I took a 3/4" piece of oil hardened drill rod and dialed it in. I then loosened the jaws and slid the drill rod out of the chuck further and tighetened the jaws again. It was still dead on as it was in the previous position. I repeated this seevral times with the same results. If you recall, this was not the case with my first ill attempt to grind the jaws.
I then had a few pieces of 4140 in various diamaeters, without doing anything other than placing them in the chuck and tightening the jaws, I was within 1 1/2 thousandths which i think is excellent for a self-centering chuck. And, since the chuck is a setrite/adjust tru, I could dial it in to almost zero if needed.
Hence my conclusion that this latest attempt at grinding was a success. I appreciate the idea of using only three jaws under normal circumstances, just curious if the setrite/adjust tru feature will work properly with only three jaws?
There is no doubt my first failed attempt was due to my flimsy 1/4" extension rod which made things worse than they were before.
As far as the carcks in the original jaws, based on the damage I see on the cross slide, it seems that careless operators ran the carriage into the chuck. The jaws are thinner at the tips on a 6-jaw chuck and they were cracked from carlessness of the operator. I do not believe it was a catostrophic accident but enough to scar the cross slide and crack some of the jaws.
Again, I thank you all for your input.