Patent ID: 8851812

Claim:
A chuck device for holding a tool having a circumferentially round tool shaft or collet, the device comprising: a) a chuck body including an annular head portion having a distal end surface, a laterally spaced coupling end section, an outer circumferential surface, and a central longitudinally extending bore with an inner circumferential bore surface to slidingly receive the tool shaft or collet with the tool axis aligned collinearly with the bore axis; b) the head portion including a first slot extending inwardly on one side of the annular head and normal to the distal end surface, and a second slot extending from the outer circumferential surface normal to and intersecting the first slot to form a stationary segment and a pivotable segment having a bore-facing, tool grasping surface that moves between a rest position and a gripping position whereby the tool grasping surface radially directs a compressive grasping force around the outer circumferential surface of the tool shaft or collet received in the bore; and c) the second slot being parallel to and laterally spaced a distance from the distal end surface sufficient to allow a threaded aperture to extend into the stationary and pivotable segments, and a tightener member to be threadingly received in the threaded aperture that is tangentially disposed between inner and outer circumferential surfaces of the head portion, and between the distal end surface and the second slot; d) the tightener member, when tightened in the threaded aperture, is effective to produce a tension force in an amount sufficient to cause the tool grasping surface to grasp the tool shaft or collet received in the bore with a compressive force in an amount sufficient to hold the tool with a slip-torque of up to about 430 inch-lbs at a rotational speed of up to at least about 20,000 rpm.