Abstract: A mandrel assembly in which the mandrel segments are expanded and contracted by means of a draw rod extending through the mandrel and driven by the same motor that rotates the mandrel during winding or unwinding operations. The draw rod is fixed for rotation with the mandrel but is movable longitudinally thereof and is provided with power threads on one end which are in engagement with complementary power threads on a nut member carried by the motor shaft. A drive gear is keyed to the nut member so that it is rotatable with the nut member but capable of movement longitudinally thereof into and out of engagement with a driven gear secured to the mandrel. A nonrotatable gear segment is mounted for shifting movement with the drive gear and moves into engagement with the driven gear as the drive gear is disengaged from the driven gear to lock the mandrel against rotation.