First, try Bill's advice to disassemble and clean the chuck. Second, disabuse yourself of the mistaken notion held by most hobbyists that a three-jaw chuck is precise. Beginning apprentices used to be taught that a three jaw cannot be relied upon for precision. That's why we have four jaw chucks that can be indicated to a within a few tenths, or precision ground collets, or turning between centers. A three jaw should be used so that all the diameters and faces of the job are turned without loosening the chuck. Everything will be within the tolerances of the spindle. Once you remove the workpiece all bets are off. When you re-insert it into the chuck you just bought all the inaccuracies of the chuck. A good one might be within a few thousanths... A not so good one might be .005 to .020 off. You pays your money and takes your chances...