A method establishing a reference point for a machine tool with X-, Y-, and Z-stages. A YZ-plane is established by reflecting a light beam off an X-stage reflector such that the light beam is sensed at an interference detector. The X-stage is moved while repositioning the head and reflector and maintaining sensing. An optical alignment module (OAM) is mounted optically perpendicular to the beam, with a bending mirror centered at the Z-axis. The Z-axis is established by setting the bending mirror to deflect the beam to the Z-axis, reflecting it off of a Z-stage reflector so it is sensed, and moving the Z-stage while repositioning the OAM relative to the X- and Y-axes to maintain sensing. An XY-plane is established by bending mirror deflecting the beam to the Y-axis, reflecting it off of a Y-stage reflector so it is sensed, and moving the Y-stage while repositioning the Y-reflector relative to the X- and Z-axes to maintain sensing.