Effects of Larger Tolerance Values

In this Question Line video, Jason answers the following question regarding the effects of larger tolerance values:

What are the potential issues with having much tighter geometric controls features that relate back to datum features that have in comparison much larger tolerance zones?  Would it cause issues with measurement repeatability?

The drawing in question, shown below, has a tight tolerance on the location of the two holes in comparison to the looser form control on the datum features.

To answer this question, Jason breaks down each feature control frame and how it to interpret it. He discusses the difference between datum features and datums, explaining that because measurements are taken from the datum plane, not the datum feature, measurement repeatability is not affected. He goes on to explain, however, that the wall thickness is affected by the amount of form error allowed for the datum features. He walks through how to calculate the worst-case minimum wall thickness for this example and what can be adjusted to obtain an acceptable minimum wall thickness.

We want to hear from you! Submit your GD&T question at the link below:

https://www.gdandtbasics.com/share-your-gdt-questions/

If your question is selected, we will notify you when our video answer is posted to our YouTube channel.

* If you are a current student, reach out to us directly and we will get you into contact with your instructor. Active students’ questions receive a direct response within 24-48 hours.