# Author: Crystal Bemis

## Metric vs Inch Dimensions and Tolerances

by Crystal Bemis on October 3, 2023.

Jason explains how to tell at a glance whether a drawing has inch or metric dimensions in this Question Line video.

## Functional Gaging and CMMs

by Crystal Bemis on September 26, 2023.

In this Question Line video, Jason compares the use of functional gages and CMMs for inspection and discusses benefits and drawbacks of each.

## 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.

## Datums, Datum Features, and Datum Simulators

by Crystal Bemis on August 11, 2023.

In this Question Line Video, Jason uses the example of a cylindrical datum feature to show how non-planar datums can be simulated and how they are able to constrain degrees of freedom.

## ISO vs ASME Position Tolerance

by Crystal Bemis on August 3, 2023.

“How do I inspect position if my drawing references ISO?” In today’s Question Line Video, Jason looks at a part with a cylindrical hole feature and compares the ASME and ISO standards for controlling the position of that hole.

## Understanding Maximum Material Condition

by Crystal Bemis on July 20, 2023.

"Why isn’t Maximum Material Condition always just the largest size the feature can be?” Jason answers our student's question and gives us a delicious way to remember the MMC state in this Question Line Video.

## 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.

## Diametric Tolerance Zones

by Crystal Bemis on June 21, 2023.

In this question line video, we explain when to use the diameter symbol in a feature control frame. The examples below illustrate the unique tolerance zones shapes and sizes for position, perpendicularity, straightness, runout, and cylindricity controls.

## Can Minimum Wall Thickness be Ensured When Using the MMC Modifier?

by Crystal Bemis on June 13, 2023.

Can you use the MMC modifier and still ensure a minimum wall thickness? To answer this question, we are going to look at a drawing of a flywheel and compare how using the MMC modifier or the LMC modifier affects the minimum wall thickness.

## 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.

## Rule #1 and Derived Median Line Straightness

by Crystal Bemis on May 30, 2023.

"Why doesn’t Rule #1 apply to the straightness of a Derived Median Line?" In this article, we look at both surface straightness and straightness of a feature of size to understand why Derived Median Line Straightness overrules Rule #1 of GD&T.

## 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.

## Surface Finish and Flatness

by Crystal Bemis on May 15, 2023.

Surface finish and flatness both limit the amount of variation in a surface – one at the micro level and one at the macro level. Is it permissible to call out both on the same surface?

## Virtual Condition vs Tolerance Zone

by Crystal Bemis on May 9, 2023.

In our video question line, our GD&T instructors answer questions submitted by our students. In this video, we answer the question, “Is the Virtual Condition the same as the Tolerance Zone?”

## Meet the GD&T Basics Team: Molly Olson, GD&T Instructor

by Crystal Bemis on April 17, 2023.

Molly Olson is one of our expert GD&T Instructors, with a wealth of valuable real-world experience in quality control and inspection. She has spent nearly 20 years as a Quality Inspector and CMM Programmer and Operator across several different industries, including aerospace, firearms, robotics, and prosthetics.

## 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: Identical Virtual Conditions for Mating Boss and Bore Features

by Crystal Bemis on March 24, 2023.

Is it allowable to have identical Virtual Conditions for mating boss and bore features? Learn how to calculate and compare Virtual Conditions of mating features to understand the potential clearance between the assembled parts.