A chuck assembly, for use with a rotary power tool, includes a chuck body rotatable about an axis, a plurality of jaws supported by the chuck body for relative movement therewith between a retracted position for permitting insertion of a tool bit within the chuck body and an extended position for clamping the tool bit, a plurality of clamping nuts surrounding the chuck body and having interior threads engageable with corresponding threads on the respective jaws, a tightening sleeve surrounding and threadably engaged with the chuck body for relative rotation therewith, and a wedge defined on the tightening sleeve for selective engagement with the clamping nuts for inwardly displacing the clamping nuts, causing the respective threads on the clamping nuts and jaws to engage, in response to rotation of the tightening sleeve relative to the chuck body in a tightening direction.