Abstract: A center finding device for locating the geometric center of a workpiece having substantially parallel side surfaces including a pair of crossed arm members pivotally secured to each other by a tubular member with a marking pin received therein and secured at one end and in slidable-pivotal relation to a longitudinal slot in each of a pair of side guide arms whereby when the guide arms are moved into engaging relation with the parallel side surfaces of the workpiece, the crossed arm members are automatically slidable into a position with the tubular member being in a geometrically centered position with respect to the workpiece. In addition, the center finding device can be used in conjunction with an accessory for locating the geometric center of a workpiece having substantially non-parallel side surfaces.