Nice chuck Ned. I am not a fan of "tommy bars" but they work and were on my very first woodturning chuck. What size screws hold your jaws Ned? They look larger diameter on the head anfd the thread than mine.
Chuck, These chucks (whew, lots of chucks here)
use the countersinks themselves to align the jaws, not the shanks of the screws. it's a more positive setup and will resist wear much longer and tend to stay tighter longer too. There isn't much you can do if a screw hole gets worn and a bit loose on a flat seat screw, but with countersuk heads you just tighten a little more and any wear is compensated for.
Aloha, Tony