A method for hard finishing two different toothings on a workpiece, wherein, prior to each machining process, to set the correct tool engagement position for the machining process, a first relative rotational angle position of a first rotational position reference of the first toothing is determined relative to an axial rotational position of the workpiece spindle holding and clamping the workpiece for the first machining, and a second relative rotational angle position of a second rotational position reference of the second toothing is determined relative to an axial rotational position of a workpiece spindle holding and clamping the workpiece for the second machining, wherein the machining operations are carried out on the same workpiece spindle with no intervening clamping change, and with the first and second rotational position references coupled to each other as the basis thereof.

A gear machining apparatus includes a rough working tool having a plurality of replaceable tool blades attached to a tool main body, such that the tool blades are arranged in a circumferential direction of the tool main body and blade tips of the tool blades are oriented outward in a radial direction of the tool main body, a finish working tool having a plurality of tool blades provided to a tool main body in a similar manner to the rough working tool, and machining controllers control to perform rough and finish machinings on the workpiece, such that the working tools are rotated on center lines in axial directions of the working tools, the workpiece is rotated on a center line in axial direction of the workpiece, and the working tools are relatively moved to the workpiece along the center line in the axial direction of the workpiece.

A combined gear cutting apparatus includes a workpiece drive portion, a first processing portion holding and moving a first tool to a processing position for a workpiece, a second processing portion holding and moving a second tool to a processing position for the workpiece, and a control portion which includes a storage portion storing workpiece information indicating a configuration of the workpiece before first processing is performed, first tool information, second tool information and relative position information. The control portion includes a tooth groove configuration calculation portion calculating tooth groove configuration information of the workpiece based on the first tool information, the workpiece information and the relative position information obtained when the first processing is completed. The second tool is configured to move to a start position of second processing for the workpiece based on the tooth groove configuration information, the second tool information and the relative position information.

A combined gear cutting apparatus includes a workpiece drive portion, a first processing portion holding and moving a first tool to a processing position for a workpiece, a second processing portion holding and moving a second tool to a processing position for the workpiece, and a control portion which includes a storage portion storing workpiece information indicating a configuration of the workpiece before first processing is performed, first tool information, second tool information and relative position information. The control portion includes a tooth groove configuration calculation portion calculating tooth groove configuration information of the workpiece based on the first tool information, the workpiece information and the relative position information obtained when the first processing is completed. The second tool is configured to move to a start position of second processing for the workpiece based on the tooth groove configuration information, the second tool information and the relative position information.