Clamping jaw

A clamping jaw (3, 6) for a clamping chuck (2) of a tool holder (1), wherein the clamping chuck (20) comprises two of the clamping jaws (3, 6) arranged spaced apart and diametrically opposite one another in a paired arrangement relative to an axis of rotation (7) of the clamping chuck (2) and configured to be moved toward and away from one another for clamping a tool shaft (11a, 11b) by advancing or retracting the clamping chuck (2) with a radial movement, wherein the clamping jaw (3, 6) has a longitudinal slot (10) having a slot mouth and a slot bottom, wherein the slot mouth opens toward the axis of rotation (7) of the clamping chuck (2), wherein the longitudinal slot (10) has transmitting surfaces for receiving positive-lockingly tool shafts (11a, 11b) of different polygonal cross-sections, and wherein the longitudinal slot (10) has slot flanks provided with the transmitting surfaces, wherein the transmitting surfaces comprise first slot flank portions provided at the slot mouth defining an approach angle (12) of 120° and second slot flank portions at the slot bottom defining a slot bottom angle (13) of 90°.