Abstract: A self-centering lathe chuck assembly for positioning and holding universal joints and associated propeller shafts comprises a pair of jaw assemblies mounted for radial movement toward and away from one another and each having a concave, conically shaped member for receiving and holding a universal joint journal cross, whereby different sizes and types of universal joints can be held in a given pair of jaw assemblies and the center or axis of the journal cross is automatically aligned with the turning axis of the lathe, thus eliminating the need for a different kit or jaw assembly for each different universal joint.