Abstract: An apparatus for measuring wall thicknesses of objects, includes a coordinate measuring machine that has a probe holder and an object support. The coordinate measuring machine is configured to provide relative movement between the probe holder and the object support in three dimensions. The apparatus also includes an ultrasonic test probe which is held by the probe holder. The coordinate measuring machine brings the transducer of the ultrasonic test probe into contact with a position on a surface of an object at the object support so that the probe can measure an object wall thickness at the probe contact position.

Abstract: A calibration block for use in calibrating a thickness gauge having a diameter d, wherein the block has a measurement face and a recess extending inwardly of the block from a face opposite the measurement face, the recess having a maximum transverse dimension at the opposite face which is not less than 3d, and in that the bottom of the recess is inclined relative to the measurement face in all directions from a central region of the bottom of the recess, the measurement face comprising a reference feature, the location of which corresponds to a specific point on the bottom of the recess.