Apparatus and method for processing screw rotor and cutting bit

A method for processing a screw rotor comprising a step of rotating a blade holder while shifting the blade holder in X-axis, Y-axis, and Z-axis directions to form a screw groove on the outer surface of a rotating cylindrical workpiece with a tool, using a processing apparatus comprising a bed;

• a C-axis shaft supporter disposed on the bed;
• a C-axis shaft held by the C-axis shaft supporter, for rotating the cylindrical workpiece;
• a column disposed on the bed;
• the blade holder rotatably held by the column;
• and the tool attached to the blade holder,
• in which said step to form a screw groove includes a first step of roughly cutting the groove on the other surface of the workpiece using a tool having an end mill and a round end mill, and a second step of shaving the left, right and bottom surfaces of the groove, wherein a shaving bit having two blades set at different angles is used for shaving the left surface and right surface, respectively, and a round bit is used for shaving the bottom surface.