Machine tool extension and method of forming the same

A method of interfacing a cutting tool which includes a generally cylindrical shank portion fabricated from a third metallic material having a third coefficient of thermal expansion to a tool holder which includes a central opening and is fabricated from a fourth metallic material having a fourth coefficient of thermal expansion, said method comprising the steps of:

• (a) providing an elongate, generally cylindrical shank member fabricated from a first metallic material having a first coefficient of thermal expansion which is less than the fourth coefficient of thermal expansion, and including an outer diameter which slightly exceeds the diameter of the central opening, a first end, and a reduced diameter second end;
• (b) heating the tool holder to a temperature sufficient to thermally increase the diameter of the central opening to a size allowing the first end of the shank member to be slidably inserted to a desired axial position therein;
• (c) allowing the tool holder to cool to ambient temperature to cause a thermal contraction of the central opening about the shank member to rigidly secure the shank member within the tool holder;
• (d) providing a bushing member fabricated from a second metallic material having a second coefficient of thermal expansion which exceeds the first and third coefficients of thermal expansion, and including an aperture extending longitudinally therethrough which is of a diameter slightly less than the diameters of the second end of the shank member and the shank portion of the cutting tool;
• (e) heating the bushing member to a temperature sufficient to thermally increase the diameter of the aperture to a size allowing the second end of the shank member and the shank portion of the cutting tool to be slidably inserted to desired axial positions in opposed ends thereof;
• and
• (f) allowing the bushing member to cool to ambient temperature to cause a thermal contraction of the aperture about the second end of the shank member and the shank portion of the cutting tool to rigidly secure the second end and the cutting tool within the bushing member.