Abstract: The present invention provides a fixture, system, and method for automatically and quickly indicating a condition of a the trunnion axis A of a computer numerically controlled (CNC) machine and optionally an alert to a machine operator. The fixture has a body preferably constructed of parallel first and second walls and a third wall disposed between, at right angles to, and connected to the first and second walls all mounted on a base. First, second, and third probe blocks are mounted on the body at first, second, and third angular positions, respectively, along an arc circumscribed by a radius about an axis of rotation. The first, second, and third blocks are mounted on an outer surface of one of the first and second parallel walls, the outer surface facing away from an other of the first and second parallel walls. The blocks include preferably co-planer respective first, second, and third flat surfaces with respective normals parallel to the axis of rotation.