This has ever happened to me in all my working years.
Somehow whilst rattling around in van vault, an sds bit has got lodged, drill point end, in the chuck!!
No means of pulling or twisting will release it!! Drill is a Hitachi.
Any ideas gents???

Ron Seal, March 2015

try getting the chuck off, if you can't get it out then buy a new chuck

merlin, May 2015