Firstly check to see if the chuck is secured with a screw, if you have a screw follow steps 1-3 else follow steps 2-3. Step 1: Screw will have a left-hand thread and must be turned clockwise to undo it. Step 2: Once the screw has been removed place a suitable Allen Key in the chuck and tighten the jaws. Step 3: You should then tap the end of the Allen Key to ease the chuck off (the chuck has a conventional thread so unscrew it in an anti-clockwise direction). Some of our high spec cordless drills will need to be serviced need to be taken to your nearest service centre to have a new chuck fitted.