Dave,
If you take the dust cover at the back of the chuck, it is usually a plastic one on these later ones, and have a look where the scoll drive gears are.
If everything is well clear of the hole, reassemble, and put the inside jaws on and put on a large ring to tighten up against. That will open up the jaws, and at the same time lock up the scroll. Then gently open it up.
If it throws the jaws off being tight whilst cutting, and then you will need to disassemble the chuck and bore the scroll and main body seperately.
John