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Category: GD&T Design and Application

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

Flatness and Rule #1

by Crystal Bemis on February 10, 2025.

In this Question Line video, Jason explains how to calculate the flatness tolerance of a surface for a given example based on the size tolerances and Rule #1.

True Position for Multiple Features

by Crystal Bemis on February 3, 2025.

In this Question Line video, Jason walks through an example where one feature control frame is controlling position for multiple features and identifies where this practice is outlined in the ASME Y14.5 spec.

Tolerances for Fillets and Rounds

by Crystal Bemis on January 27, 2025.

In this Question Line video, Jason discusses applying tolerances to fillets and rounds, explaining why applying profile of a surface allows more direct control of the size and form than using +/- tolerances.

Profile Unequal Zone

by Crystal Bemis on December 9, 2024.

In this Question Line video, Jason discusses the ISO Unequal Zone (UZ) modifier, which is similar to the Unequally Disposed modifier of the ASME standard. He walks through an example where the UZ modifier is included in a feature control frame controlling profile of a surface and discusses how this impacts the tolerance zone.

Positional Control of X, Y, and Z

by Crystal Bemis on December 2, 2024.

In this Question Line video, Jason discusses the positional control of the X, Y, and Z translations for a cylindrical post on the submitted drawing. He defines the datum reference frame and zero point of the part and explains why the feature control frame in question is essential to constraining where the cylinder exists vertically.

How to Find Zero

by Crystal Bemis on October 21, 2024.

In this video, Jason shows how to find the zero, or origin, for a given feature control frame. He walks through an example drawing that utilizes a single datum reference frame, describing how the datum reference frame fully constrains the part, noting that more complex parts may utilize multiple datum reference frames, resulting in multiple origin points.

Datums for Castings

by Crystal Bemis on September 9, 2024.

In this Question Line video, Jason discusses how datum targets, datum reference frames, and multiple datum structures can be of assistance in casting drawings.  

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.