Mounting device for cutting tool, tool body and cutting tool

A cutting insert mounting system adapted for a cutting tool in which, by screwing a tightening screw into a screw hole of an insert mounting seat of a tool body through a through hole of a cutting insert, the cutting insert is detachably mounted on the insert mounting seat, wherein

• the insert mounting seat has a bottom wall surface and at least two side wall surfaces extending so as to intersect the bottom wall surface;
• the screw hole intersects the bottom wall surface;
• a central axis of the screw hole is inclined with respect to a normal direction of the bottom wall surface;
• when the cutting insert is placed on the insert mounting seat, on a first virtual plane defined so as to expand the bottom wall surface, a first passage point of the central axis of the screw hole is shifted to at least either one side of the at least two side wall surfaces from a second passage point of a central axis of the through hole;
• and
• when a shift direction of the first passage point of the central axis of the screw hole from the second passage point of the central axis of the through hole on the first virtual plane is defined as an axis shift direction, and a direction of a virtual line obtained by projecting the central axis of the screw hole onto the first virtual plane is defined as an inclination direction,
• the axis shift direction and the inclination direction are different directions.

In combination, a tool body having an insert mounting seat and a cutting insert having a through hole provided with an insert central axis (B), wherein the insert mounting seat comprises:

• a bottom wall surface defining a first virtual plane (P);
• first and second side wall surfaces extending so as to intersect the bottom wall surface, imaginary extensions of the first and second side walls converging to define a vertex at an intersecting portion, as viewed in a direction opposite the bottom wall surface;
• a screw hole intersecting the bottom wall surface, the screw hole having a screw hole central axis (A) which intersects the first virtual plane (P) at first passage point (Pa), the screw hole central axis (A) being inclined at a first inclination angle (F) with respect to a normal line (L1) to the first virtual plane (P), the normal line (L1) intersecting the screw hole central axis (A) at the first passage point (Pa);
• a second passage point (Pb) being defined by the intersection of the insert central axis (B) with the first virtual plane (P), when the cutting insert is placed on the insert mounting seat and abuts the first and second side walls;
• an inclination direction (A1) being defined by a virtual line obtained by projecting the screw hole central axis (A) onto the first virtual plane (P), as viewed in said direction opposite the bottom wall surface;
• an axis shift direction (A2) being defined by an imaginary line (L2) extending between the second passage point (Pb) and the first passage point (Pa), as viewed in said direction opposite the bottom wall surface;
• and wherein:
• the inclination direction (A1) and the axis shift direction (A2) are different directions with a first angular difference (E) therebetween, as viewed in said direction opposite the bottom wall surface.