Abstract: This invention relates to high speed spindles employing a tool holding mechanism which rotates with the spindle. In machining applications utilizing high speed spindles which operate above 20,000 RPM, it is desired to manufacture such spindles so that they maintain their balance. Spindles which employ tool holding mechanisms are required to grasp and release tools between machining operations. Such mechanisms usually employ springs for either holding tools in a collect or returning the release mechanism. This invention discloses two types of springs which are true flexures and are held integral with the spindle shaft. The nature of the design is such that it affords the minimal amount of structural position deviation after each actuation for tool changes, thus minimizing out-of-balance conditions.