A temporary part is mounted onto the chuck of the diamond turning machine. A diamond turning tip of the diamond turning machine is used to form a reference surface on the temporary part, registering a baseline for a motion control system of the diamond turning machine. While the temporary part remains mounted to the diamond turning machine, a workpiece is mounted onto the temporary part, and the diamond tip is controlled relative to the reference surface to diamond turn a surface profile on the workpiece. Because the baseline established by the reference surface compensates for positional variations from mounting parts directly onto the chuck of the diamond turning machine, the length of the workpiece can be shaped to a designated length with a high degree of accuracy.