Tool holder

A rotary tool holder for detachably retaining a rotary tool in a tapered bore of a spindle, the rotary tool holder comprising:

• a shank having a tapered outer surface corresponding to the tapered bore, the shank having a front contact portion and a rear contact portion;
• a flange adjacent the front contact portion;
• a first circular cantilever adjacent the front contact portion, the first circular cantilever having a fixed end and a free end, the free end extending toward the flange;
• a second circular cantilever adjacent the rear contact portion, the second circular cantilever having the free and fixed ends, the free end extending toward a rear face of the shank;
• and
• wherein rotation of the rotary tool holder when disposed in the spindle results in the free end of each of the first and second circular cantilevers expanding radially under the influence of centrifugal force such that the free ends maintain contact with the tapered bore which also expands under the influence of centrifugal force during the rotation.

A rotary tool holder for detachably retaining a rotary tool in a tapered bore of a spindle in which the tapered bore has a taper defined by a front diameter and a rear diameter which is smaller than the front diameter, and wherein the front and rear diameters each change at different rates under the influence of centrifuigal force when the spindle is rotated such that the tapered bore has a different taper at different speeds of rotation, the rotary tool holder comprising:

• a shank having a tapered outer surface, the tapered outer surface having a taper defined by a first diameter and a second diameter which is smaller than the first diameter, the first and second diameters each changing at different rates under the influence of centrifugal force when the shank is rotated in the spindle such that the tapered outer surface has a different taper at different speeds of rotation;
• the first diameter generally corresponding to the front diameter of the tapered bore when disposed therein and the spindle is rest;
• and
• wherein the second diameter is selected to cause the tapered outer surface to have an optimized taper when the shank is disposed in the spindle and rotated within a certain range of speeds, the optimized taper substantially corresponding to a taper of the tapered bore within the certain range of speeds such that improved contact between the tapered outer surface and the tapered bore results within the certain range of speeds.