Abstract: A machine tool, in particular multi-spindle turning machine, comprising a machine frame, a turret body being rotatably supported by the machine frame, a plurality of workpiece spindles being arranged on the turret body, each of the workpiece spindles having a workpiece receiving portion for receiving a respective workpiece on one side of the turret body facing a working space of the machine tool, and a plurality of tool post assemblies supported by the machine frame around the turret body, wherein each tool post assembly includes a tool post having one or more tool cartridge receiving openings respectively being configured to detachably receive a tool holder cartridge TC holding a tool.

Abstract: A production method for a ring-shaped part is provided with: an inner cutting step for reciprocating a first cutting blade in the radial direction D4 from a state of contact with the center of the thickness of one end 91a of a rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the inner circumferential R1-side of the cylindrical blank 91; an outer cutting step before, after or simultaneously with the inner cutting step for reciprocating a second cutting blade in the radial direction D4 from a state of contact with the center of the thickness of the one end 91a of the rotating cylindrical blank 91 and moving toward the other end 91b in the axial direction D1 to form a semicircular track while cutting the outer circumferential R2-side of the cylindrical blank 91; and a separation step after the inner cutting step and the outer cutting step for cutting the portion 92 of the cylindrical blank 91, the inner circumferential R1-side