My new bosch cordless drill chuck doesn,t have a screw in it how do i remove the chuck ?

The greatest one that fit most chucks are 13mm but remember to remove the torxscrew (in clockwise direction) inside the chuck first and if you use a new chuck beware of to use some loctite on the screw.
The long side in a vice the short in the chuck and turn the left anticlockwise direction the L direction and pull short but fast the trigger and move the drill in the same direction turning the drill has priority to make doing this in a very short time. to not overcharge you tool.

There is supposed to be a Phillips head LH thread screw in the chuck. I have seen the screw head worn down so you can no longer get a screwdriver to work.
We usually cut the chuck off with a metal chop saw just at the screw - thread what remains of the chuck off, which usually leaves 1/4" of the screw sticking out of the spindle - remove with vise grips.
Its not an easy prospect when that happens.

Make sure it is in low gear on drill mode. try with just a bar in the socket and hit the end to shock it. This is sometimes better than a constant force.

remove the old one. check inside the throat of the chuck to see if it has a screw. if it does turn it left to right. if no screw good. take a very large allen wrench and place in chuck tighten it. place it on a flat surface, bench edge, where the chuck is free. lift the allen wrench up higher than level and take a large hammer and hit it down hard. this will break it loose from the spindle. when you go back with the new one put never seize or grease on it some it won't bind. next time you change it it will come off easier.

Use of both is the same:
- loosen "chuck" (part where bit is installed).
- insert bit (hand tighen chuck so that bit is secured)
- tighten chuck securely with chuck tool, or by holding rotating chuck with hand and pulling trigger (GENTLY or you will shave off skin!)
- put drill in forward or reverse mode and pull trigger to inser or remove screw / drill hole.

ensure that battery is charged on cordless drilll.
squeeze connectors to remove and place in charger when battery is too low to operate drill.

The dc925 and the current model dcd950 along with several other models of Dewalt 's line of cordless hammer drills DO NOT have a screw inside removal requires a CHUCK REMOVAL FIXTURE part #
233804-40 also you can't use a generic replacement chuck. As of 2/2/2010 the prices on the Dewaltservicenet web site are $72.74 for
the tool and $69.70 for the chuck, part # 330075-90.

This drill has a keyless chuck. Put your bit in the chuck and hold the collar of the chuck while pressing the trigger in the forward position. To undo the chuck do this in reverse. You can also hand tighten the keyless chuck if you prefer. I have a 1/4' adapter that I keep in my drill so I can change bits quickly.

The screw you are trying to remove is left hand thread. You must turn is clockwise to remove it.
Hope this helps

You must remove the inner chuck retaining bolt first, it is a torx screw and is left hand thread. once you have this screw out, get yourself a 1/2" allen key (the L kind). Chuck the short end in the chuck to grip it, use a mallet to hit on the long end (this will unthread the chuck). The spindle thread is regular Right hand thread. It may take a few good hits to knock it loose but it will come off.

Put the screw back in the chuck, tighten it up then back it out 1 turn. Take a punch, put it in the chuck and give it a quick hit with a hammer. That should do the trick.