A vibration damping toolholder for a metal cutting tool, the toolholder including a holder body provided with an internal cavity, which extends inside the holder body along the longitudinal axis, and which has a first cavity end at a first holder body end. The damping toolholder further includes a tuning mass, which is movably arranged inside the cavity and extends along the longitudinal axis, and which has a first tuning mass end at the first holder body end. The damping toolholder also includes a damping medium, which surrounds the tuning mass inside the cavity, and a single primary spring element, which is positioned inside the cavity. An outer spring element end is immovably fixed to a first cavity end at the longitudinal axis, and an inner spring element end is immovably fixed to the first tuning mass end at the longitudinal axis.

A headstock structure of computer numerical control milling and boring machine tool comprising a spindle, a conducting slip ring, a rotating plate, a mobile unit, two balancing units, a driving unit, and a cutter locking unit; the conducting slip ring being sleeved on a top end of the spindle; the rotating plate being rotated in horizontal direction under the drive of the spindle; the mobile being rotated in horizontal direction together with the rotating plate; the two balancing units being located on the rotating plate; the driving unit being configured to drive the mobile unit to perform horizontal radial movement; the cutter locking unit being configured to lock the cutter, so that the headstock structure can rotate and move up and down, and can perform horizontal radial motion.

A headstock structure of computer numerical control milling and boring machine tool comprising a spindle, a conducting slip ring, a rotating plate, a mobile unit, two balancing units, a driving unit, and a cutter locking unit; the conducting slip ring being sleeved on a top end of the spindle; the rotating plate being rotated in horizontal direction under the drive of the spindle; the mobile being rotated in horizontal direction together with the rotating plate; the two balancing units being located on the rotating plate; the driving unit being configured to drive the mobile unit to perform horizontal radial movement; the cutter locking unit being configured to lock the cutter, so that the headstock structure can rotate and move up and down, and can perform horizontal radial motion.