In this case, two pins are to be tested with a diameter of 18.75 mm, which have the h6 tolerance of 13 µ (0 / -0.013) with a nominal dimension of 18.75 mm, which is too small a tolerance range for most optical scanners.

Most of the other items that the customer wants checked are in larger dimensions. Here the problem arises for the measurement technician that a larger measurement field also means greater measurement noise. And that is then too big for the two high-precision pins.

So one solution to this situation would be to manually measure the pin diameter using a micrometer. These 1D gauges are very common and reliable, the good ones giving results with very small spreads around 1 µ or less.

A well-known manufacturer of these devices is the family owned company Mahr from Esslingen, which has been producing high-precision measuring equipment for over 160 years.

But how can you 'install' such a tactile measurement in an optical GOM Inspect project without great effort?

Let's say we want to inspect a straight pin named 'Datum C1'.

We create it as a nominal auto feature from the CAD using the 'Construct/Cylinder/Auto-Cylinder (nominal)' commands. Via the properties (Tab key) we assign it a specific length, e.g. 10 mm, since the program sets it to a length of 1 mm by default.

Since it does not yet have a measurement principle, it is initially displayed in red and receives the red icons that tell us that its creation is not yet complete.

Now we check the diameter of the cylinder on the component using the micrometer, with the result of 12.007 mm. We note this length.

In GOM Inspect we then create another cylinder via the 'Construct/Cylinder/Point-Direction-Cylinder' menu.

For the construction elements we click twice on the already existing nominal cylinder Datum C1.

For the size 'Radius by value' we now enter the previously noted value of the diameter / 2 = 6.0035 mm and click on 'Create and close'.

Next we convert the manual cylinder we just created into an actual feature using the 'Operations/Elements/Convert to Actual Element' command line.

The manual cylinder C1 12,007 manual then changes color and turns green, having now become an actual item. Its label has disappeared, so let's make it visible again via the properties.

In order to assign a measurement principle to the nominal cylinder Datum C1, we open I-Inspect and select 'Link to actual element' from the list of measurement principles, and then from the list the cylinder C1 12.007 we just created.

Finally, it is sufficient to carry out a diameter check for the new nominal/actual pairing.

Using I-Inspect, select the 'Diameter' check for the 'Date C1' element, which you name eloquently.

The result is then saved in a report page, which is supplemented with a meaningful comment to point out the special feature of the manual measurement source we have used here.