I can't get this chuck off. I cut it in half since I couldn't get it to spin at all. There appears to be a Phillips headed screw on the end. I tried going both clockwise and counterclockwise. I used an impact driver too. I bought this hammer drill for $10. Its a Craftsman Professional 9-26726 Made in Italy.
To remove an old chuck, remove the left-handed screw down in the bottom (open up the chuck jaws to their maximum), insert a sturdy old large allen wrench into the chuck itself and start the drill in reverse, allowing the allen wrench to intermittently smack something very stable and solid, i.e. a concrete slab. WEAR EYE PROTECTION! That loosens the chuck up quickly. To install a new chuck,, simply reverse the procedure and run the drill forward to tighten, intermittently smacking the slab to tighten. Secure with the screw whose threads are almost always left-handed. In the rare event that procedure doesn't work, it might be an odd-ball drill chuck that uses left-hand threads on the shaft so in that case you would simply reverse the drill direction accordingly.
But, since you cut the chuck in half, I don't see how you can get enough torque to hold the spindle and shaft securely and twist the chuck off by hand.
Well the chuck jaws couldn't move. I tried the allen key method and it didn't work. I was going the right direction too. I saw the screw inside the chuck and though that I could use an impact driver to turn it but I don't think it is a movable screw. I guess the drill is garage unless I find a replacement part. I'll keep you updated