Diaphragm chuck

A diaphragm chuck comprising an operating element inserted in a chuck body and axially movable in relation to the chuck body, a diaphragm fixed to a free end of said operating element, said diaphragm being secured to the chuck body its outer circumference;

• three base jaws disposed in a driving connection with said diaphragm, on each of which a centering surface is disposed in a concentric alignment with an axis of said operating element;
• three clamping jaws attachable to corresponding ones of said base jaws, by means of which a gear to be machined can be clamped, and which make contact with the centering surface,
• and clamping pins, each allocated to one of said clamping jaws, and radially aligned and arranged between two teeth of a gear in the clamped condition,
• wherein a centering groove is disposed in said base jaws and said corresponding clamping jaws, a key is disposed in each of said centering grooves, and a cross-sectional shape and arrangement of said key is adapted to a pitch (T) of the gear to be clamped, such that the position of said corresponding clamping jaw is adapted to be changed by said corresponding key in relation to said centering groove in said base jaw concentrically to a middle point of the gear;
• and
• wherein one of said three keys is provided with a T-shaped cross section and said two other keys are provided with an S-shaped cross section, the two S-shaped keys being disposed in said centering grooves of said base jaw, and said clamping jaws are disposed in a mirror-image offset arrangement in relation to one another.