The block (10) has a guiding bracket (12) guiding a coupling part (21), and including upper and lower stops (14, 13) limiting rotational displacement of the coupling part. The coupling part is supported against the guiding bracket by a slide. The guiding bracket is traversed by a hole in which a coupling part element is positioned. The coupling part has two V-shaped arms (22) that are connected with respect to one another by a crosspiece that is supported against a front surface of the guiding bracket, and by the coupling part element.Le bloc de travail comporte une pièce dattelage (12) montée libre en rotation sur son avant.Il porte une crosse de guidage (12) de ladite pièce dattelage (21) et des butées basse (13) et haute (14) de limitation du déplacement en rotation de ladite pièce dattelage (21).
