Drill chuck problem - solved.

I had a rather an odd problem with this chuck for my fancy big drill that I wanted to use on the lavatory floor the other week, the jaws would only close part of the way so I scratched my head, put it aside for a while and used the other drill.
Anyway I went to disassemble it today and found the screw under the jaws had become loose, loose enough that the jaws closed onto its head. The fix couldn't be simpler, just tighten it but be aware that chuck screws in my experience always have left hand threads, so tightening them is an anti-clockwise operation.