I'm having trouble removing the chuck from my Ryobi drill (about 10 years old, 430W, model details and manual lost, 3/8 inch chuck key, chuck made in Germany, maximum bit capacity 10 mm, with electric cord). In the centre of the chuck (when it is wide open) there is what looks like a screw head with a large round dip in the middle. My screwdrivers are useless on it and I suspect I'm doing something wrong. Can you please help?

Fred Schwartz, January 2005

screw in middle of chuck is probably left hand thread so turning screw clockwise will undo. you need to remove this screw.
with screw removed insert short end of biggest allen key you have into chuck and tighten. Whack allen key with rubber mallet anti clockwise

rob, June 2005