The Black and Decker PS1800 uses a two-sleeve keyless chuck for holding the drill bit. In order to tighten the chuck you firmly grip the inner ring with one hand, while turning the outer ring clockwise with the other hand. Tighten the chuck as much as possible before use. Also make sure that the drill bit is securely between the teeth of the chuck and not at an angle. If the drill bit still will not tighten then the chuck could be bad and will need to be replaced.