Abstract: An electro-mechanical dynamic datum point locator tool is provided to determine x and y axes datum points on a workpiece. The locator tool is a cylinder for placement, for example, in an adjustable chuck in a mill head of a milling machine. A cylindrical tip assembly depends from the cylinder and is flexibly supported for eccentric to concentric rotation during contact with the edge of a workpiece which is held in place on the bed of the milling machine. During rotation of the locator tool, a light emitting diode emits light from the circumference of the cylinder whenever the initially eccentrically placed cylindrical tip touches the edge of the workpiece. As the edge of the workpiece is moved closer to being in line with the centerline of the mill head of the milling machine, the cylindrical tip is reactively moved progressively toward its concentric rotating position.