how do i change the drill bit on my avid power 3/8 keyless chuck? it's stuck.

Don't force it—you can damage the chuck. It's likely stuck because of dirt or because it was overtightened during last use.

Diagnosis: Debris in the chuck jaws or metal galling from overtightening.

Fix:

1. Put on a pair of work gloves for a better grip.
2. Set the drill's direction selector to REVERSE.
3. Hold the chuck sleeve firmly with one hand, and grip the drill body with the other.
4. Squeeze the trigger in short bursts. The reverse action should loosen the jaws. If it starts to move, stop using the motor and finish opening by hand.

If that didn't work: Apply a penetrating oil (like WD-40) around the base of the chuck where the jaws retract. Let it sit for 10 minutes, then try the reverse-trigger method again. As a last resort, you can gently tap the chuck sleeve with a rubber mallet while trying to turn it, but be careful not to hit the drill body.

Heads up: To prevent this, always clean the chuck and bit shank before inserting. Don't overtighten by using the drill's power in forward to tighten—use the reverse-tighten method described in another answer, or just hand-tighten firmly.