In the world of engineering and manufacturing, we say that GD&T gives us the ability to explicitly describe both nominal geometry and its allowable departure or tolerance from that nominal value. One side of the convention allows for the definition of the geometry and the other allows for the definition of tolerance. Accomplishing the definitions […]

Today our featured GD&T term is “features,” which includes “features of size.” But before we jump into this we need to talk about a basic term or thing or maybe we’ll call it a concept, which is the term part. In GD&T a part needs to be thought of as an item, or two or […]

In GD&T basic dimensions used to be a fairly simple thing to define. However, today, among other things, “Basic dimensions” are numbers on an engineering drawing that represent values of size in whatever the measurement system being used on the drawing is. Those values are used to describe the theoretically exact size, profile, orientation or […]

Today we’re going to look at the concentricity control. This control is used a lot in a variety of situations that involve coaxial relationships. The definition states that concentricity controls ‘all’ diametrically opposed elements of a figure of revolution. Breaking Down the Basics Let’s break that down and look at a few rules for this […]

Today I want to talk about a common definition for something we all talk about when the subject of GD&T comes up. I think it’s safe to say that the vast majority of people reading this series earn their livings on the floors of American factories. We design, machine, assemble, weld, measure, probe, form, punch, […]

With the previous topic, Rule #1, we discussed the need for a guiding principle to govern the need for geometry to follow rules that allow things to fit under all conditions, given that the proper engineering has been established for the condition being considered. That principal was stated as “size controls form.” In it the […]

Today our featured GD&T term is “feature control frames.” We at Metalcraft decided some time ago to put together a glossary of sorts. It will be alphabetized in proper fashion but as various terms are added they will not be added in A to Z fashion, but more in order of importance, or more importantly, […]

Rule #1. In the world of engineering drawing there is an infinite amount of complexity to be detailed. All over the world there are parts and mechanisms that are dreamed up every day and for many of them there is a need for the assurance that a particular design will be flexible enough to work […]

Actual Mating Envelope – The Basics Actual mating envelope is a term that refers to a machined / manufactured part’s feature of size “as is” condition. To define what that means specifically, we need a specific individual part to talk about. The reason for that is when you have a part, or bunch of parts, […]