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Category: GD&T Design and Application

Articles related to design concepts or application of GD&T to engineering prints

True Position on Bolt Circle Diameters

by Crystal Bemis on June 21, 2024.

In this Question Line video, Jason walks through a drawing that includes a position control on a pattern of holes (bolt circle), explaining what the feature control frame is and is not controlling.

Reference Dimensions on True Position

by Crystal Bemis on June 17, 2024.

In this Question Line video, Jason walks through an assembly drawing to explain the scenario where a feature being controlled by position must have a reference size dimension rather than a tolerance on the size of the feature.  

Composite Profile Control

by Crystal Bemis on June 3, 2024.

In this Question Line video, Jason discusses a composite feature control frame controlling profile tolerance. He walks through through the user submitted examples to explain the controls of each frame.

GD&T Position for Bidirectional Control

by Crystal Bemis on April 4, 2024.

The position symbol is one of the most useful symbols in GD&T - but did you realize that you can use it to allow more tolerance in one direction and less in another? In this video, Jason explains how to achieve bidirectional position control through the use of a Multiple Single Segment Feature Control Frame.

Position vs Coordinate Dimensions

by Crystal Bemis on January 17, 2024.

Geometric Dimensioning and Tolerancing, and the concept of “True Position,” originated due to a rejection of functional parts as a result of coordinate dimensioning. Let’s look at a simple assembly to illustrate why this is true, and how GD&T Position takes care of this problem.

Designing to MMC and LMC

by Crystal Bemis on August 30, 2023.

In the Question Line Video below, Jason answers a student’s question regarding whether a feature of size can be designed to both Maximum Material Condition (MMC) and Least Material Condition (LMC) boundary constraints.

Control on Multiple Profiles

by Crystal Bemis on July 7, 2023.

Is it possible to control multiple identical profiles by including a multiplier with the feature control frame? In the video below, Jason reviews a drawing with 2 irregularly shaped identical cutouts to answer this question.

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.

Sheet Metal Holes as Datum Features

by Crystal Bemis on May 16, 2023.

If I specify a hole in a practically thin feature, such as a piece of sheet metal, is this still considered a cylindrical datum? Is this a poor choice of datum? In this article, we look at an example to help us answer these questions.