How to Change a Drill Chuck
A drill chuck is a part of a drill that wears out very easily, making changing drill bits very difficult. If the chuck is worn, the teeth will not hold the bit in place.
Open the drill chuck all the way and look at the inside for the retaining screw.
Using a screwdriver remove the screw. Most chuck screws are left threaded, so turn the screwdriver clockwise to loosen the screw and not strip the screwhead.
After you have removed the retaining screw, you will see a hex screw. Place a large allen wrench into the hex screw and tighten the drill chuck around it.
Using a hammer or mallet, tap the extended end of the allen wrench. Turn the allen wrench counterclockwise and loosen the hex head bolt. The hex head bolt is usually extremely tight, so it may feel like it does not want to release. You may need to have someone help you hold down the drill while you hit the allen wrench with the hammer or mallet. With the hex head bolt loosened, remove the drill chuck.
Using a correctly sized new drill chuck, install the new one by reversing the steps above (tighten the hex head bolt, tighten the retaining screw, close the drill chuck).