Rotary cutting tool assembly and cutting insert and tool shank therefor

A rotary cutting tool comprising:

• a tool shank having a first end portion and an opposite second end portion, said first end portion being configured to be inserted into a tool holder, said opposite second end portion having a recess and a drive surface adjacent said recess;
• and
• a cutting insert comprising:
• a body portion having a first end, an opposite second end, and a central axis, the opposite second end of said body portion inserted into the recess of the opposite second end portion of said tool shank;
• and
• a driven surface extending from said body portion generally away from said central axis, said driven surface comprising:
• a central portion;
• a first portion of generally planar shape extending away from said central portion in a direction generally toward the first end of said body portion;
• and
• a second portion extending away from said central portion in a direction generally transverse to said central axis,
• wherein said central portion comprises a curved surface transitioning between the first portion and the second portion of said driven surface and wherein a portion of said driven surface is engaged by a corresponding portion of said drive surface.

A tool shank for a rotary cutting tool, said rotary cutting tool comprising a cutting insert comprising a body portion having a first end, an opposite second end, and a first central axis, and a driven surface extending from said body portion generally away from said first central axis, said tool shank comprising:

• a generally cylindrical body having a first end portion, an opposite second end portion, and a second central axis, said first end portion structured to be inserted into a tool holder, said opposite second end portion comprising:
• a recess structured to accommodate the opposite second end of said cutting insert;
• a drive surface adjacent said recess, said drive surface comprising:
• a central portion;
• a first portion of generally planar shape extending away from said central portion in a direction generally away from said cylindrical body;
• and
• a second portion extending away from said central portion in a direction generally transverse to said second central axis,
• wherein said central portion comprises a curved surface transitioning between the first portion and the second portion of said drive surface and wherein a portion of the central portion of said drive surface is structured to engage a corresponding portion of said driven surface.