Guys...
As far as chucks... Here's a few thoughts/opinions from yours truly:
6", 3J scroll and 8", 4J independent chucks cost about the same amount and can range from about $175 to $700. That's a huge price range! Is there a difference between one costing $175 and another costing $700? I should hope so but, do not know the answer because all my chucks are in the $175 to $250 range. I'm quite happy with them. With a little fine tuning, they all balance well and the jaws are nice and even. If I had to guess, an expensive chuck will not need to be balanced and the jaws probably do not need to be tweaked for straightness (but I wouldn't hold my breath). If you mount an expensive chuck to a backplate, you'll still need to do fitting on the interfaces.
I guess there are set-tru chucks... -Don't see the need for that because when I tune my chucks, they're as good as any chuck will ever be. When they were new, they were a little stiff -but a couple months later, they weren't stiff anymore. I supposed I could have deburred the components -but at the risk of doing more harm than good... My expectations of a chuck are not high. If it repeats within a few thou, it's good. If I need better repeatability than that I'll use collets or spin between centers.
My collet chuck is steel and my jawed chucks are semi-steel. Given the nature of how jaws operate, I don't think making a jawed chuck out of steel will make it work any better or last any longer...
I just don't understand what's so great about an expensive chuck. The chucks that came with my lathe are perfectly fine once they were fitted properly.
Ray