A tool holder apparatus for a press brake is provided. The apparatus comprises a support plate having a first receiving surface. A pivotable clamp has an engagement portion that is moveable toward the first receiving surface of the support plate by pivoting the clamp. The engagement portion has therein formed a bore in which a lifting shaft is rotatably received. The engagement portion defines an opening communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the opening by an exterior corner of a forming tool. The notch is configured such that when the engagement portion of the clamp is forced against such tool, a first surface of the exterior tool corner bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against a second surface of the exterior tool corner and delivering to the tool a mounting force having a component normal to the second surface of the exterior tool corner.