Abstract: A neutralizable permanent-magnet base is shaped to engage the usual housing for the gear-supporting mandrel of known types of gear cutters. A U-shaped yoke fixed to the top of the base supports a pivot block on a transverse horizontal axis. The pivot block receives a sliding cylindrical arm for rotational and length adjustments. A probe head on the front end of the sliding arm carries a ball or other-shaped probe which can be swung downwardly between gear teeth before removal, then upwardly to permit gear removal for testing, again downwardly to accurately re-locate the gear if found defective but salvageable, and finally upwardly for the re-cutting of one, several or all of the teeth of the defective gear.