4-Jaw work holding chucks

A 4-jaw work holding chuck, comprising a body provided with two pairs of oppositely disposed radiating guides, a jaw slidably adjustable along each said guides, a pair of adjusting screws extending diametrically across the body and threadedly connected to oppositely disposed pair of jaws, each adjusting screw having a right hand thread at one end and a left hand thread at its other end whereby, as the screw is turned, the oppositely disposed pair of jaws concerned are adjusted in position with equal and opposite movement, a sleeve located on at least one end of at least one of the adjusting screws between said screw and the associated jaw at said one end, said sleeve being internally screwthreaded for engaging the screwthread at that end of its associated screw and externally screwthreaded for engaging the associated jaw whereby rotation of said sleeve provides a differential adjustment of its associated jaw relative to the opposite jaw independent of said adjusting screw.