Toothed tool coupling for rotating a rotary tool

In combination:

• a driven tool defining an axis of rotation and including a body having at least one seat for receiving a cutting insert;
• a drive member for driving the tool about the axis;
• and
• a securing element for securing the driven tool to the drive member;
• the driven tool including a driven part rotatable about the axis, and the drive member including a drive part rotatable about the axis and mated with the driven part to form a drive coupling therewith,
• the drive part and the driven part being conical as viewed in a longitudinal section plane containing the axis, and being arranged one inside of the other,
• the driven part including driven teeth projecting generally radially with respect to the axis and received in respective radially-open recesses formed in the drive part;
• each of the driven teeth terminating in an axially facing wall and including a sidewall contacting a sidewall of the recess, a curvature of the tooth sidewall being different from a curvature of the recess sidewall at locations where those sidewalls contact one another, wherein such contact is in the form of a point contact on each side of a generally radial line of symmetry of the respective tooth as viewed in a direction parallel to the axis;
• each of the contact points being operable to transmit a drive force from the drive part of the driven part in a respective direction of rotation;
• each of the contact points defining a tangent line, wherein the drive force is transmitted along a line of force oriented perpendicular to a respective tangent line;
• wherein a driving angle is formed between the line of symmetry and each tangent line, each driving angle being in the range of −5° to +45°;
• wherein the driven teeth project from a first axially facing surface of the driven tool;
• the recesses being formed in a second axially facing surface of the drive member;
• the first and second axially facing surfaces opposing one another and spaced apart axially to form a first axial gap;
• each of the teeth terminating axially in a first axially facing wall;
• each of the recesses terminating in a second axially facing wall;
• the first axially facing walls opposing respective second axially facing walls and spaced therefrom to form respective second axial gaps larger than the first axial gap.