Abstract: A coordinate measuring machine is described including a vertical probe shaft mounted on an X-axis carriage in turn mounted on a Y-axis carriage for movement along three orthogonal axes, in which the Y-axis carriage is guided and supported on a first guide beam fixed extending along one side of a machine base with air bearings mounted to the lower end of one upright engaging all four sides of the first guide beam. The Y-axis carriage is also supported on a second guide beam fixed extending along the other side of the base, with air bearings mounted to the lower end of the other upright engaging only the top and bottom surfaces. A lower crossmember beam connects the lower ends of the upright to increase stiffness of the Y-axis carriage. A cast aluminum table is supported on the base with three cast in support features projecting from the underside, configured to minimize thermal distortion, with a steel plate bonded into a recess in the upper surface.