In order to meet any special requirements regarding measuring speed (large number of geometric elements on the hob cutter; production stoppage due to measurement, etc.), linear-drive coordinate measuring machines are preferred. The swiveling sensors make it possible to view the threads of the hob cutters. Many parameters of the hob tooth’s cutting edge (i.e., the base pitch and the profile form) can be measured optically with high precision. The face parameters and slot pitch are measured with mechanical styli (Fig. 62). This set-up makes it possible to measure and inspect the profile of several hundred teeth in just a few minutes.

Another problem occurs when measuring grinding wheels and dressing rolls. Their effective geometry is not defined by a single cutting edge but rather by the superposition of numerous cutting elements (grains) when the grinding wheel is turned. The effective contour is also measured using optical coordinate measuring machines with rotational axes. This is done by measuring the contours of grinding wheels and dressing rolls in various rotational positions and then, based on the measured data, mathematically superimposing a circumscribed envelope.

One type of workpiece typical for optical coordinate measuring machines is an indexable insert. The cutting edges of this tool element were formerly measured using measuring microscopes and measuring projectors. Today this measuring task is performed perfectly by image processing coordinate measuring machines. High-speed scanning is combined with maximum precision. ToleranceFit® software represents an especially suitable evaluation technique. The cutting radii are decisive for the service life of the tools and the quality of the final products. A Foucault Laser Sensor and the 3D-Patch software represent an ideal combination for measuring radii with lengths of only a few micrometers. The 3D-Patch also offers the advantage of being able to measure a large number of points simultaneously.

Optical coordinate measuring machines used for tool measurement are also used to perform direct correction of the manufacturing process. For example, it is possible to measure the contours of step drills with optical coordinate measuring machines and then compare the results with the CAD data. In a manner similar to the one described above for wire EDM, correction data can be generated for the tool grinding process and then fed directly to the controller of the grinding machine. This makes it possible to fulfill even the highest precision requirements for tool manufacture.