The Black & Decker drill model KD574CRE has a keyless chuck. When the chuck becomes stuck it is usually because it heated and tightened during use, but was allowed to cool before opening was attempted. WD40, if left for a few hours to penetrate, may help, but in my experience it usually does not make enough of a difference. A rubber jam-jar opener will help. If you don't have one, wrap several loops of thick rubber around the chuck, this will provide extra leverage. Using rubber gloves will assist even further. As a last resort, use the drill excessively until the chuck heats up, then try the one of the rubber options (above) before it cools down.