Chuck

A chuck comprising:

• a chuck body rotatable about a chuck axis and formed centered on the chuck axis with a passage;
• a center support on the chuck body;
• an axially movable center carried in the support on the axis;
• a plurality of pivots angularly equispaced about the axis in the chuck body and defining respective pivot axes all lying generally in a plane perpendicular to the chuck axis and extending generally tangentially of a circle centered on the chuck axis and lying in the plane;
• an actuating sleeve axially shiftable in the passage;
• a piston disk coupled to the sleeve, having a frustoconical outer surface centered on the chuck axis and axially shiftable in the body by the sleeve;
• respective shafts journaled in the pivots, rotatable therein about the respective pivot axes, and each having an outer surface portion that is frustoconical and centered on the respective pivot axis;
• and
• respective levers fitted to the frustoconical surface portions of the shafts and each having
• a front arm projecting axially forwardly from the shaft out of the chuck body and adapted to carry a tool-gripping jaw, and
• a rear arm projecting axially rearwardly from the shaft and operatively engageable by the outer surface of the disk, whereby axial movement of the actuating sleeve shifts the disk against the rear arms and pivots the front arms radially inward to grip a workpiece and center it on the axis.