Coupling mechanism for cutting tool

A cutter member for use in conjunction with a shank member wherein the shank member has an axial forward end and a shank bore opening at the axial forward end, the shank bore having an axial shank bore length, the shank bore containing a female threaded portion and an axial rearward shank bore portion axially rearward of the female threaded portion, and the axial rearward shank bore portion having a terminal end;

• the cutter member comprising:
• an axial forward end and an axial rearward end, a cutting region at the axial forward end of the cutter member, and a male threaded portion adjacent the axial rearward end of the cutter member;
• an axial forward radial aligner portion axially forward of the male threaded portion, and a flat axial stop shoulder axially forward of the axial forward radial aligner portion, and an arcuate fillet joining the axial forward radial aligner portion and the flat axial stop shoulder, and the arcuate fillet having a radius wherein the ratio of the radius of the arcuate fillet to the maximum diameter of the cutting region ranges between about 0.02 and about 0.04.