So I've been working on a 1963 Colchester Triumph with an L1 tapered spindle. It came with two Pratt chucks. A 9"-10"ish 3 jaw and a larger 12" 4 Jaw. I haven't mounted the 4 jaw yet but I have had the 3 jaw on and off during the moving of the machine. I remounted the chuck and noticed it had some notable runout. So I thought maybe I hadn't installed the chuck correctly. I removed it with the spanner, and then cleaned everything very well to make sure there were no chips or anything in the way and remounted it and it appeared to have even worse run-out. Did it one more time and the run-out seemed less. I did notice that the jaws were a bit mangled on the chuck and that one of them is quite sloppy in the grooves of the scroll. When eye balling the back of the chuck it appears the step down groove has a bit of a wobble to it. The OD of the truck runs true within .003" on an indicator. Is there a process that is advised for installing the chucks? Draw it up and tap around? Or is it possible that this chuck is just old and abused? I've found a few L1 blank backing plates and some cheap chinese 10" and 8" chucks... don't know if I want to go that route and spend the money on a new chuck when I'm just doing something wrong here.