Chuck is stuck OPEN black and decker power drill

Open the chuck as wide as it will open and look inside to see what type of screw/bolt it uses then using the correct tool insert it into the chuck and undo the bolt/screw, usually it will have a left hand thread so to unscrew it needs to be rotated in a clockwise directions, hold the chuck tightly but dont use excessive force if this does not work then try unscrewing it in the opposite direction, at all times be firm but like I mentioned earlier dont use excessive force.

two pairs of multigrips
one on e chuck and the other on the bit that does the turning to tighten on the drill bit.

If the chuck is stuck open and you cant "muscle" it closed something is probably jammed up in there and it needs to be replaced. Chucks take a good share of the abuse on power tools and most manufactuers consider them a "common wear item" like brake pads or Tires on your car. A chuck is fairly simple to replace if your drill stuck open and they are commonly replaced on the higher end "Industrial Grade" Power Tools like DeWalt and Milwaukee.
Looking at the Make and Model of your drill it would probably be easiest and most cost effective to just replace the entire drill. If you tried to replace the chuck and found a chuck that will fit your tool it may cost you anywhere from $25 - $40. For Around $40 you can purchase a new drill with a fresh battery.

Look at the three jaws in the chuck,if on is further out than the others the you need to tap ti back into place with a small punch and a hammer.If this does not work then you need to replace the chuck,remove the screw at the bottom of the chuck[where you put the bit],then you will need to to clamp vise grip on the chuck and with it pointed away from you hit the vise grips with a hammer with a sharp blow downward and it should come off.Hope this helps.

Make sure you try it in both directions.

the chuck is broken inside if clicking. Ace and True Value stores sell chuck replacements

put some oil in the chuck and see if you can free it up buy turning it back and forth let it set with the oil for a day or so to let the oil soak in.

Try putting a vise grip on the bit,, and a big vise grip or chanel lock wrench on the key lock..

That should break it free..

Good luck..

I'd put penetrating oil in it and tap the chuck with a plastic hammer. That should free it up.

Best rgrds, W/D

if chuck is wide open ,look down inside there should be an allen screw or bolt at the bottom of the chuck it should undo anti clocwise and the chuck comes off