Chuck assembly

A chuck assembly system comprising a chuck assembly body for clamping a working tool and an operational jig for operating said chuck assembly body, characterized in that said chuck assembly body includes a tool clamping portion provided with an opening portion for clamping the tool and a sleeve portion for widening/narrowing the opening portion, a taper portion is provided on at least one of an inner circumferential wall of said sleeve portion and an outer circumferential wall of said tool clamping portion, said tool clamping portion and said sleeve portion are brought into contact with each other at the taper portion, a retainer portion for retaining the operational jig is provided on said sleeve portion, a support portion is provided in a predetermined position of said chuck assembly body for supporting the operational jig retained at the retainer portion, the operational jig slidingly moves said sleeve portion, said sleeve portion retained by the operational jig is slidingly moved relative to the tool clamping portion when the operational jig is lever-operated in a taper direction of the taper portion by using the support portion as a fulcrum, and the opening portion of the tool clamping portion is widened/narrowed by taper action of the taper portion by the sliding movement of the sleeve portion.