Abstract: A winding tool for engaging the sprocket of a magnetic tape cassette which is of unitary construction. It has an elongated body which includes a handle portion and a blade portion. The blade portion is tapered downwardly to the end of the winding tool and has a pair of diametrically opposed keys or flutes which fit into the space between adjacent sprocket teeth, and which is dimensioned to bear against the end surface of the sprocket teeth and the interior surface of the sprocket when the blade portion is inserted into the sprocket about one-half of its length.