Abstract: The Invention is an apparatus for squaring a spindle of a machine tool with a work holding surface. A shank is adapted to be connected to the spindle. The shank has a shank axis and is attached to a body. The body has a lower side from which depends a reference point. The reference point defines a measurement plane perpendicular to the shank axis. A first gauge having a spaced-apart relation to the reference point has a range of measurement that intersects the measurement plane. The range of measurement falls on a measurement axis parallel to the shank axis.