How to remove a dr200 BLACK & DECKER 3/8" DRILL CHUCK, no chuck screw in chuck

screw in the chuck great 10 or 13 mm allen key short end in chuck and counter clockwise (but remember of the screw in the chuck if there is one (cometimes ) remove this screw clockwise but the chuck after that counterclockwise and in case there is no screw then make a little bit warm because of locktite on the threaded spindle can be used. the fixation of the spindle is the point about how to fix it so thats give no problem thats not to say by Black &decker machines because of the quality .
a blow with the hammer on the long end of the Allen key while the machine is in 1st gear or the long end in a bench -vise (short end of it in the chuck and rotate and turn on the machine to left.
More possibilities with a possibillity to fixated the spindle with a wrench in a bench -vise if there is an option to.

Screw in side Has Left hand threads

Remove the left hand screw from inside the chuck and then insert the chuck key onto the chuck, place the machine on a suitable work surface and give it a wack so that the chuck will unscrew off the drill anti clockwise.

If it won't close the only other option you have is to break the outer collar and use a chisel to hit on the exposed jaws inside the chuck. I have detailed instructions in the tip section on how to remove a chuck from these drills. Let me know if you need more assistance.

There is an 2 types of chuck ether it is an screw type or not..If your drill chuck is an screw type it is easy to remove if it is not you must have a special tools to remove it.

open the chuck all the way then look in and you will see the head of a screw take that out .
then you need to hold the arbor some how so you can un screw the chuck from the shaft.

remove the chuck retaining screw LH thread, and then find a bent handle allen wrench about the chuck capacity and insert the shorter piece in the jaws and tighten, Shift the tool to the low position (if it has one) and the selector to drill only (if it has one) position the chuck on a block of wood at about a 30 degree angle so you can strike it counter clockwise and hit it with a hammer, it might take a couple times but it will come off. Reinstall in reverse order,

There is a screw in the bottom of the chuck. It has a standard thread. Clamp the chuck in a vise, find a screw driver that fits as snug as possible, to prevent stripping the screw, remove the screw and pry off the chuck. An impact driver will simplify the removal, if one is available.

There are one-way (non-reversible) and two-way (reversible) drills. Mine is one-way. Methods for chuck removal are different for these two types.
Procedure for one-way (non-reversible) drills:
Drills of this type have no chuck screw, so one have to hold the spindle with a wrench, than to sharply strike the wrench with a hammer to spin it off.
Procedure for two-way (reversible) drills:
Open the chuck up and in the bottom is a screw that holds the chuck on the shaft.The screw turns in a clock wise motion to be removed and then you can top the chuck off the shaft.

If you say that the chuck can not be tighten only, then I would say that the left thread screw that keeps the chuck to the tool have become unloosen and can not allow the chuck to be tighten. The remedy for that is to unloosen the chuck as much as you can, then tight the left thread screw but rotating it left till the bottom and then the chuck will work. All the above if the chuck can not be tighten...