The jaws should be clamped down on something at the front of the jaws, not the back; if you do it at the back and the jaws are somewhat loose in the chuck body, you will end up with the same situation that you have now, maybe less, but the same. If your chuck has solid (not two piece) you can drill holes in the end face of the jaw with a carbide drill, insert pins into the holes and clamp down on a steel ring and reach through the hole in the ring to grind the ID of the jaws; if you have two piece jaws, short pieces of allen wrench can be cut and inserted into the allen bolts and likewise clamp down on a ring.