Abstract: Apparatus is provided for opening and closing the jaws of a chuck without the use of a key. This invention is particularly suitable for improving a standard drill chuck so that tools can be easily and rapidly changed without the use of a drill chuck key. In one embodiment of the invention, the first ring element containing a pair of dogs is slidably mounted to the collar of the drill chuck. When the drill is activated and the first ring element is in an upper position, its dogs engage opposing dogs on a stationary second ring element. Relative rotary motion is thereby achieved between the jaws and the collar of the drill chuck which, in turn, tightens the jaws about the tool. Resilient means are provided for yielding to allow the first ring element to be pushed downward by the action of the opposing dogs when the jaws have closed about the tool.