How do I remove and reinstall the chuck?

To remove the chuck, insert a 5/16 in. or larger hex key into the chuck and tighten the jaws, then tap the hex key clockwise with a mallet to loosen the internal chuck screw (which has left-hand threads), and remove the screw by turning it clockwise. Then tap the hex key counterclockwise to loosen the chuck from the spindle so it can be unscrewed by hand. Always lock the switch trigger by placing the direction of rotation selector in the center position before beginning this process. (Page 14)