A device for reducing the otherwise minimum unthreading distance between the end of a bobbin and an unthreading guide in a textile yarn unthreading machine. The device comprises a member which defines a formed edge surface, preferably in the form of a circular disc, mounted substantially perpendicular to the axis of the bobbin and concentric with this axis. The disc is positioned between the bobbin and the unthreading guide to define a specially shaped, yarn supporting edge. The positioning of the disc is such that, as the yarn passes over the edge of the disc while being unwound, the angle formed by the straight line which joins the edge of the disc and the facing edge of the bobbin relative to said axis is equal to the half-angle of unthreading. Further the angle formed by the straight line which joins the edge of the disc to the unthreading guide, relative to the said axis, is markedly greater than the half-angle of unthreading.