Multi-function machine tool and machining method in multi-function machine tool

A machining method of a multi-function machine tool comprising,

• a main spindle which is rotatably disposed on a bed of the machine tool, and has workpiece attachment means for attaching the workpiece on the tip end thereof,
• a tool rest main body which is disposed movably in relative terms in a first linear direction parallel to the axial line of said main spindle, and in a second linear direction perpendicular to said first linear direction,
• and a turning tool rest which is disposed on said tool rest main body, which allows a mounting of a tool, and which is disposed so said turning tool rest can turn relative to said tool rest main body about a turning axis which has an axial line oriented in a direction that is perpendicular to both said first linear direction and said second linear direction, said machining method comprising the steps of:
• setting a center position of a turning motion that said tool mounted on said turning tool rest is caused to perform, in an arbitrary position that differs from the position of said turning axis;
• determining a circular-arc motion based on the relative motion of said tool rest main body in said first linear direction and said second linear direction that is necessary in order to cause said tool to perform said turning motion;
• and
• performing the machining of said workpiece by causing said turning tool rest to perform said turning motion about said turning axis, causing said tool rest main body to perform said circular-arc motion concurrently and synchronously with said turning motion of said turning tool rest, and causing said tool to perform said turning motion about said center position.