Abstract: A self-tightening drill chuck has a chuck body adapted to be mounted on a drill spindle for rotation about an axis and a tightening sleeve surrounding the body and formed with a substantially frustoconical seat centered on the axis and having a front end turned away from the chuck body and formed with a plurality of radially inwardly open, angularly offset, and axially extending grooves. The sleeve is secured on the chuck body for rotation about the axis thereon but against axial movement thereon. A jaw guide in the sleeve formed with a plurality of axially forwardly open and angularly spaced slots has a front end formed with respective radially outwardly projecting ridges engaged in the grooves. Respective jaws are axially and radially displaceable in the slots and on the seat.