These chucks are specifically designed to hold large diameter thin walled components, Aluminium components of Turbines and Couplings, Precision Railway wheels and large size Gear blanks of Earth moving equipments. Normally these chucks are manufactured in size above 500 in diameter for mounting on vertical lathes. But smaller size chucks up to 250 dia also possible to be manufactured against specific requirements.
In this Design of chuck, there are always three pairs of Jaws (Total six Jaws). Each Jaw is inter-linked and pivoted with the other in the pair in such way that when one touches the component, the other swings on the pivot to touch the component according to the component. This pivoting does not permit the Jaw to exert undue pressure at one gripping point. In doing so the deformation of the component is avoided or reduced to tolerable limits.