If it is that stubborn I would just open the drill and remove the chuck assembly and put it in a vice as if heating (a good idea) but unfortunately some Black and Decker use a plastic gear that may melt. Once out if it can't be moved just replace the chuck from a Black and Decker stockist.
sparky, December 2005
Are you turning the chuck in the right direction? you might be tightening the chuck
Godfrey Webster, December 2005
You could try heating the chuck and cooling the chuck to see if this would free it up. IE use a pint stripping gun or blow torch then cool in a bucket of water. The expansion and contraction might work. Don't over do it mind. Or maybe a good soak in WD40 or the likes.
