Rotary cutting tool, rotary cutting unit, and rotary cutting method

A rotary cutting tool comprising:

• a body without a back taper, the body having a flow path of a cutting oil inside the body;
• and
• a cutting edge part integrated with the body, the cutting edge part having at least one first supply port that supplies the cutting oil toward a workpiece,
• wherein the body has at least one second supply port that supplies the cutting oil to a clearance formed between a bush for positioning and the body, the bush being used by inserting the body, and
• wherein the cutting edge part is integrated with the body at a distal most end of the body, and the cutting edge part has a proximal end that is distal to a distal most positioned second supply port, and an outlet of the at least one first supply port opens out in an exterior region of the cutting edge part,
• wherein the cutting edge part has a diameter that is larger than the body at a border region where the body meets the cutting edge part,
• wherein the body includes a shank as an opposite end to an end at the border region, and a cutting edge part side portion adjacent to the end at the border region,
• wherein a diameter of an entirety of the cutting edge part side portion is substantially constant to such an extent that the cutting edge part side portion has no back taper,
• wherein the cutting edge part side portion has the at least one second supply port, and
• wherein the flow path of the cutting oil is branched to a first flow path and a second flow path, and the cutting oil is supplied to the at least one first supply port through the first flow path while the cutting oil is supplied to the at least one second supply port through the second flow path.