Even expensive 3-jaw chucks in good condition are a poor choice when repeatability matters. Griptru maybe, which are adjustable. A 3-jaw is speedy, but the price is repeatability, which drops off as the jaws, slots and scroll wears.
Better alternatives available. I put an independent 4-jaw chuck on when I need repeatability, because the job can be accurately centred with a DTI. Some machinists always work with a 4-jaw, because, with practice, work can be centred quickly and repeat error eliminated. Collet chucks are the bees-knees for certain workflows, I have an ER32 collet chuck which is very useful at times, but if I was serious 5C collets are better because they can hold shapes other than round. A full set of 5C collets is expensive.
My hex collet block iand 3-jaw are moderately repeatable, but test yours to find out how good or bad yours is in your chuck. I don't think scraping the block is a good idea, because repeatability depends on what's wrong with the chuck : probably better to replace the chuck, or the jaws, or grind the jaws.
Main use of hex and square collet blocks in my workshop is moving work between mill, lathe and bench, not overcoming of my 3-jaw chuck's limitations. Good for what it does, but that doesn't include accurate repeatability.
Dave