Methods, systems and tools are provided for controllable adjustment of a removal rate of cutting edges of rapidly rotating effectors of manually-guided material- and tissue-separating tools without significantly changing the rotation speed of the effectors or the position, orientation or the geometry of the effectors, and in particular, for precisely maintaining work space boundaries during material and tissue removal with effectors in rapidly rotating machine tools in surgery and freehand manufacturing to produce free-form surfaces. The manually-guided material-separating and tissue-separating tools and effectors allow controllable adjustment of the removal rate of the material-separating cutting edges of the effector by mechanically adjusting a position or orientation of at least one cutting edge cover at a constant rotation speed of the effector without appreciable change of the removal movement.