Abstract: The present invention entails a mandrel for a winding machine having a fixed flange that is adapted to be secured to a spindle of the winding machine. A core is secured to one end of the fixed flange and includes a plurality of core segments that are pivotally connected at one end to this fixed flange and include a series of projections at the opposite end and wherein the core segments are movable between expanded and collapsed positions. The mandrel further includes a removable flange having a circumferential groove adapted to mate with the projections on the core segments when the core segments are in the expanded position. Finally, the mandrel includes a guide member mounted to the inner surface of the removable flange for engaging the core segments and moving the core segments to the expanded position when the removable flange is moved in an axial direction towards the fixed flange so that the projections on the core segments are aligned with the circumferential groove in the removable flange.