A tool for a coil (1) of a continuous object (2), having a central hole (6) running axially through it. In accordance with the invention the tool comprises a central part (9) for insertion into said central hole to be activated for internal cooperation with the coil. The central part comprises an elongate body (10) defining a centre line (13), a central bearing means (14) defining an axis of rotation that coincides with the centre line of the body, a plurality of peripheral engagement members (15) distributed around said centre line and spaced from it, a carrying member (55) connected to the body (10) and carrying the engagement members (15), and one or more power members (16) to actuate the engagement members for friction engagement with the inner side of the coil to form a rotatable unit (17). The invention also relates to such a central part.