Abstract: A corner locator for aligning machine tools comprises a metal sphere with a section removed. The section has the shape of either a right angled corner, which is bounded by three mutually perpendicular planes, or a wedge bounded by two intersecting planes. The three-plane version in use fits onto a corner of a rectangular workpiece, and the two-plane version in use fits onto an edge. In either case all planes bounding the removed sections pass through the exact center of the sphere. With the locator in place, the spindle of the machine tool may be set at any angle whatsoever relative to the faces of the workpiece, and the machine tool spindle axis aligned to pass through the center of the sphere as follows: insert a dial indicator gauge into the spindle; bring the gauge arm into contact with the sphere; rotate the spindle while moving the spindle along the machine axes to locate the point of minimum runout. At this point the spindle axis points directly toward the center.