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Category: GD&T Design and Application

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

Symmetric Parts and GD&T

by Crystal Bemis on August 29, 2024.

In this Question Line video, Jason walks through a user-submitted symmetric part drawing. He discusses why the drawing is incorrect and how to fix it, noting that the symmetry symbol was removed from the ASME Y14.5 standard due to common misuse of the symbol.

Reliable Datum Features

by Crystal Bemis on August 6, 2024.

In this Question Line video, Jason discusses reliable datum features. He explains that unreliable datum features can be avoided by following the functional intent of the part and walks through two drawing examples to explain the thought process behind selecting datum features.

When to use DML Straightness

by Crystal Bemis on July 23, 2024.

In this Question Line video, Brandon walks through examples for both surface straightness and derived median line straightness, explaining how to correctly apply them and discussing design and inspection considerations.

When to Use DMP Flatness

by Crystal Bemis on July 18, 2024.

In this Question Line video, Brandon explains the application of derived median plane (DMP) Flatness and discusses its frequent misuse and potential issues when used for stacking parts. He also provides an alternative for controlling flatness for stacking or symmetrical parts. 

When to Use MMC and MMB

by Crystal Bemis on June 25, 2024.

In this Question Line video, Jason reviews a drawing example to explain when Maximum Material Condition and Maximum Material Boundary modifiers may be applied.

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.