Cutting insert and cutting tool

A cutting tool comprising a plurality of cutting inserts and a holder which holds the plurality of cutting inserts, the plurality of cutting inserts comprising:

• a first end surface which forms a regular polygonal shape in a plan view;
• a second end surface facing an opposite direction with respect to the first end surface;
• a peripheral side surface connecting the first end surface and the second end surface and provided with a plurality of peripheral side surface parts formed in rotational symmetry with respect to a central axis which penetrates the first end surface and the second end surface;
• and
• a plurality of cutting edges respectively formed in connecting parts between the plurality of peripheral side surface parts and the first end surface, wherein:
• the second end surface is provided with a recess comprising a plurality of inclined surface parts which respectively have a normal intersecting with the central axis and which are formed in rotational symmetry with respect to the central axis, the inclined surface parts being equal in number to the peripheral side surface parts;
• in an end view seen from a direction facing the second end surface, an angle formed by the normal of each of the inclined surface parts which passes through the central axis and a normal of the peripheral side surface part through which the said normal passes, wherein such normal passes through the central axis, is different from an angle formed by the normal of the said inclined surface part and a normal of the peripheral side surface part adjacent to the said peripheral side surface part, wherein such normal passes through the central axis;
• the holder comprises a plurality of insert pockets for respectively holding the plurality of cutting inserts;
• each of the plurality of insert pockets comprises a first wall part for coming into contact with one of the plurality of peripheral side surface parts of the cutting insert to be held, a second wall part for coming into contact with another one of the plurality of peripheral side surface parts, a ceiling part for coming into contact with the first end surface, and a bottom part for coming into contact with the second end surface;
• the holder is provided with a plurality of through holes each of which is provided, so as to be opened in the bottom part, with a female thread for screwing with a male screw formed in a pin for pressing the inclined surface part of the cutting insert held in the insert pocket, said pressing to be made in a direction of the first end surface, wherein the plurality of through holes corresponds to the plurality of insert pockets;
• and
• an axis of the female thread formed in each of the plurality of through holes is parallel to a normal of the inclined surface part which passes through the central axis, the inclined surface part being pressed against a bottom surface of the pin to be screwed into the female thread.