A tool holder has a first holder part for inserting into a receptacle in the machine tool and a second holder part for holding a tool. The piezoelectric device is configured to produce an acoustic wave to assist the separation between the mirror plate and the object. The alloy barriers protect surrounding materials from oxidation during oxidative recrystallization steps and protect cell dielectrics from loss of oxygen during high temperature processing steps. The retraction pedal permits downward rotation of the guide head from its raised blocking position to its lowered non-blocking position when the retraction pedal is in its second position, and blocks downward rotation of the guide head from its raised blocking position to its lowered non-blocking position when the retraction pedal is in its it first position.