# Tag: Datums in GD&T

## Locating Datum Features

by Crystal Bemis on June 5, 2023.

Why doesn't a feature of size that is indicated as a datum feature need to be located? In this article and corresponding question line video, we look at two drawing examples to illustrate why datum features are not located.

## Common GD&T Student Questions: Perpendicular Datums from Imperfect Features

by Crystal Bemis on April 6, 2023.

How can datums be perfectly perpendicular to each other when the features themselves are likely imperfect? The feature axis and the datum axis derived from the feature are found in two different ways, using the Unrelated Actual Mating Envelope and the Related Actual Mating Envelope.

## Common GD&T Student Questions: A Pattern of Holes as a Datum Feature

by Crystal Bemis on March 28, 2023.

We often see a pattern of holes indicated as a datum feature in a GD&T drawing. How do we simulate this to create our datum reference frame?

## Common GD&T Student Questions: A Single Point as a Secondary Datum

by Crystal Bemis on March 17, 2023.

Can a single point (without clocking) be used as a secondary datum in a feature control frame? To answer this question, we first need to determine what datum feature is being represented by this single point. Read on to discover the answer to this commonly asked question from our GD&T students.

## Using a Complicated or Curved Surface as a Datum

by Tom Geiss on June 11, 2020.

In this question line video – Tom discusses how to understand a curved profile surface as a datum for 4 holes that are required to remain normal to the irregular surface. How do we do...

## Can GD&T Flatness be used on a Datum?

by Tom Geiss on May 18, 2020.

Check out this question brought up about Flatness in our GD&T Fundamentals Course. We get a lot of questions about when flatness can be applied and how datums can be used with this. There are...

## Datum Feature

by GD&T Basics on December 23, 2014.

A datum is theoretical exact plane, axis or point location that GD&T or dimensional tolerances are referenced to. You can think of them as an anchor for the entire part; where the other features are referenced from. A datum feature is usually an important functional feature that needs to be controlled during measurement as well.