A drill-chuck body is rotatable about an axis and formed with a plurality of passages opening axially rearward at a rear face of the body and radially outwardly at windows in a side of the body. Jaws displaceable between front and rear positions in the passages each have a row of teeth exposed radially outwardly at the respective windows. A tightening ring rotatable about the axis is formed with an internal screwthread engaged at the windows with the teeth such that rotation of the ring moves the jaws between the front and rear positions. A tightening sleeve fitted around and coupled rotationally to the tightening ring extends axially rearward past the windows. This brace ring is radially inwardly engaged with the body and engages radially outwardly between the windows and the rear face with the tightening sleeve so as to coaxially center it on the body.