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What are GD&T tolerances?

GD&T tolerances allow for determining and assessing geometrical deviations of parts. They describe the maximum permissible deviations from the nominal state of a part. If GD&T tolerances are exceeded, the function, accuracy of fit or form of the part is not fulfilled. The tolerances can be used to determine whether a bore hole is manufactured to fit exactly, whether it has the correct direction or whether existing form errors are within the permissible limits, for example. GD&T tolerances are used throughout all steps of the process chain, such as design, production and quality control.

Possible causes for GD&T deviations are, for example:

• Deformation during processing
• Wear and tear of the tool
• Machine vibration
• Temperature fluctuations during processing

GD&T Functions in GOM Inspect Suite

While GD&T tolerances are used for specification in design, they help the metrologist to verify a part. The basic prerequisite for efficient evaluation is full-field measuring data generated by optical measurement technology. GOM Inspect Suite includes several GD&T functions for a comprehensive analysis of dimensions, form and position by means of datum systems, fitting elements and tolerances. The parametric design of the GOM software additionally supports and facilitates GD&T analyses. For measuring and analyzing the individual elements, this means that every element only has to be constructed once and can then be used as a reference. The respective computation method is set automatically.