Abstract: A tool holder incorporating a tool position compensating mechanism is disclosed, which includes a screw shaft axially slidably but non-rotatably supported in a tool mounting shell and formed with a cam surface. A rotary member is rotatably received and threadedly engaged with the screw shaft. A ring shaped internal gear and a reduction gear device including a planet gear are arranged to transmit rotation of a tool spindle to the rotary member at a predetermined reduction gear ratio. When rotated, the rotary member moves the screw shaft in the axial direction which causes adjustment of a tool position in the radial direction by the wedging action of the cam surface.

Abstract: A machine tool includes an automatic tool change device for changing a tool between a tool change position on a tool storage magazine and a spindle by a tool change arm. A pair of guard covers are arranged between the tool change position and the spindle to be pivoted in a horizontal plane. A drive means is provided for normally maintaining the guard covers closed and for opening the guard covers to permit a tool change operation.