Cutting tool for machining differential case, machining apparatus for differential case and machining method for differential case

A cutting tool for machining a differential case, the cutting tool being attached to a machining apparatus and used to perform cutting on a spherical inner surface of a differential case,

• the cutting tool comprising:
• a shaft part;
• a semicircular cutting edge integrally and immovably fixed to the shaft part and laterally protruding from the shaft part;
• a fixing part formed at one end side of the shaft part and that is for fixing the shaft part to the machining apparatus;
• and
• a retaining part formed at the other end side of the shaft part and that is for retaining the shaft part to be retained by the machining apparatus, and
• the differential case comprising:
• a cylindrical part;
• shaft holes being a pair of through-holes in a side surface of the cylindrical part;
• a pair of openings in the side surface of the cylindrical part;
• and
• a pair of axle holes at an upper and lower portions of the cylindrical part,
• wherein the cutting tool is configured to perform cutting on the spherical inner surface of the differential case where the shaft holes are provided without rotating the shaft part and the semicircular cutting edge while rotating the differential case integrally with a rotary body of the machining apparatus fixed to the differential case when the shaft part and the semicircular cutting edge fixed to the shaft part are inserted into an inside of the differential case through one of the pair of openings in a both-ends-held state in which both the fixing part and the retaining part are supported by the machining apparatus.