In this video I test 3 jaw, 4 jaw and 6 jaw selfcentering scroll chucks, and two collet chucks.
By finding the best position on the spindle and find the best keyhole, you can get really good precision and low runout, even with these relatively cheap parts.
In this video I show the difference when you find the correct position and if you not, and I also show how I got the chucks to match the spindle, because that was not plain sailing.