Bosch keyless chuck stuck

not much can be done as the chuck is not specifically designed to handle hammer drill operations (they crack the scroll thread adjuster inside )
best get a new chuck and if you do a lot of hammering get a proper hammer drill that has a push in operation not an ordinary electrical drill with a hammer capability

There are SDS type chucks, both key and keyless, available commonly. Any large hardware store or specialist power tool shop will have them.

http://toolguyd.com/blog/wp-content/uploads/2014/02/Bosch-Keyless-SDS-Drill-Chuck.jpg
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Can not see what model you have. Is it a keyless chuck or an SDS chuck? With a keyless chuck hold the machine in a vice by the drill bit. now tap the chuck with a hammer or pin punch & hammer. DONOT hit the chuck on the jaws gut on the rim around them. I have had success using this method. If it is an SDS type chuck pull the chuck cap up as far as possible along the bit them if there are any ring springs you will have to try remove them then slide the sleeve up the bit, now you should be able to remove any steel balls. If the bit does not come out now hold bit in vice as before and tap on tool holder.

Try holding the bit in a vice and gently tap the chuck off of the bit and see it it releases the pressure on the jaws.

use some kind of lube like liquid wrench or wd40 and let it set for a bit. Then tap it with anything like a wrench, hammer, etc.

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.

Tap it with a hammer, gently.....

Hi,
Soak it with WD-40 and let set so the lub goes down into the chuck and then try later...

heatman101

open jaws for large size bit.look in bottom and there will be a screw slot or phillips head screw or possibly an allen head screw.remove this,by possibly turning clockwise. and then chuck up a large allen wrench. try removing the chuck by tapping wrench with hammer. this may be threaded on counterclockwise.have to try both ways.

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

Best rgrds, W/D