The degree to which the sub-micrometer pitch measurement accuracy of a gear-measuring instrument (GMI) can be evaluated is limited when using a gear artifact. We propose a new method of evaluating GMI pitch measurement accuracy using a sphere artifact, where the sphere is treated as a tooth flank. In this paper we report (i) the design of the sphere artifact, (ii) a method of measuring the sphere artifact with a GMI, (iii) a method of evaluating pitch measurement accuracy based on a self-calibration technique or a comparative measurement technique, and (iv) the results of evaluating GMI pitch measurement accuracy using a sphere artifact. Sub-micrometer evaluation was found to be possible. (C) 2012 Elsevier Inc. All rights reserved.