Ade,
Anywhere between 0.001" to 0.003" is about average on a new reasonably priced chuck.
Once the scroll and jaws become worn, as yours surely are, then the scrapman cometh. Unless you are forever going to be doing roughie jobs, and always truing up the piece first using larger material.
As Ned has stated, I broached the idea a few years back and people didn't believe me, until they tried it for themselves and couldn't fathom out why it worked, but it does. In fact the first thing I do when fitting a new chuck is try it in all bolt positions first to get the least runout, then try to find which keyhole gives the best results then mark that up. Invariably, if the hole has a zero on it, that usually is the best one. I think it is something they do in the factory during manufacture, they always use the same keyhole as they set the parts up for machining and assembly.
In your case, I think new chucks might be in order, they have had their day.
John