Chuck of the indexing type

A chuck of the indexing type for holding a large workpiece weighing up to about 2,000 pounds comprising a pair of substantially planar support plates rigidly interconnected in spaced parallel relationship and consisting of a base plate and a top plate having an enlarged central aperture of sufficient size to readily permit passage of a workpiece therethrough, a pair of opposed jaw supports mounted between said plates adjacent the periphery of said aperture, a housing for each of said jaw supports fixedly positioned and rigidly supported between said plates, one of said jaw supports being slidably movable within said housing relative to said plates toward and away from the other support, said jaw supports including live centers positioned coaxially along the axis of movement of said movable support, a jaw mounted on each live center for indexed rotation relative to said supports into any one of a number of indexed rotary positions, a jaw support operator mounted on the housing between said plates and having wedge-like drive means in alignment with said live centers for driving said movable support and associated jaw toward and away from said other jaw and support for clampably engaging and releasing a workpiece positioned between the jaws, and jaw locking means supportably mounted on the base plate and directly engaging the jaws to provide support for the jaws in a direction normal to the base plate and directly opposite machine tool pressure on the workpiece, said locking means rigidly immobilizing the indexed jaws against rotation and readily releasing the jaws for indexed rotation.