Hi Dan,
It is quite simple to replace your chuck, first you have to open your chuck jaws wide enough to remove the left hand threaded screw on the inside of the chuck, which should be a torx T20 (clockwise loosen). These are often tight, as they are put in with threadlock, once you have removed the screw, tighten an allen key - as big a one as you can manage to get into the chuck, with the long end sticking out, then hold the drill with the chuck facing away from you, and the allen key facing to the right hand side, then strike the allen key with a hammer, until it unscrews, then simply get your new chuck, screw it on and replace the centre reversing screw, it may take a while to come loose, as they are quite tight, but it will come eventually!!!
Dave the tool repairer, September 2007
