Black & Decker reverse the drill comes off - Black & Decker Drills

SOURCE: inserting new drill bit

Assuming that it is this drill:

http://www.toolpartsdirect.com/cgi-bin/schematic.cgi/blackdecker/7144-04_TYPE_4

You will need a chuck key - hopefully you have that with the drill. It's a little t-shaped bar with a cog on one end. You put it into the holes in the chuck (the part at the end which grps the bit) and turn anti-clockwise to open the jaws. Place a bit in the centre and then turn it clockwise to tighten. Tighten the bit using each of the three holes in the chuck and make sure you remove the chuck key before you use the drill - keep it safe!

SOURCE: I have the black and decker hammer drill model

look at the back of the brush holder for a tab that the forward/reverse lever locks into, it might be broken not allowing it to shift.

SOURCE: am trying to remove a drill chuck head please

Open the jaws all the way, inside there is a Left handed screw, meaning you turn it clockwise to remove it. With that out the chuck unscrews counter clockwise, You may need to put the short end of an allen wrench in the chuck and then hit the allen wrench with a hammer/mallet to break it loose. Reverse to reinstall

SOURCE: black and decker cd12c cordless drill Charger

I would guess 12 volts

SOURCE: HOW DO I LOOSEN A KEYLESS CHUCK TO REMOVE A DRILL

Keyless chucks normally have a knurled ring at the base of the chuck that you hold in one hand while turning the large knurled taper with the other. If the chuck has been overtightened, and you cant open like this, try using two stilson wrenches (Pipe wrenches) one on each of these parts. Use a soft cloth in the jaws to avoid damaging the knurling. You can also try some Q20 or similar into the chuck to help lubricate it.