Abstract: A chuck for equipping a rotary machine includes a body intended to be fixed to a drive shaft of the machine, in which there are mounted several jaws which slide in bores converging forward and which each have an outwardly facing threaded part, a sleeve being pivotably mounted on the body and having an interior wall which collaborates with a nut itself engaged with the threaded exterior part of the jaws. The body includes, in its region covered by the nut, a peripheral set of teeth and the nut bears locking means which are intended to engage in the set of teeth of the body when the chuck is in the tightened position, and which are intended to be activated by the sleeve. The sleeve has an angular relative movement with respect to the locking means between an unlocked position in which the sleeve turns the nut and a locked position in which the chuck is in its tightened position.