Geometric Dimensioning and Tolerancing, more commonly known by its shortened name, GD&T, is a method of communicating manufacturing information. It uses a system of symbols, definitions, and conventions to describe how large a part is supposed to be, its form, orientation, location tolerances, and other dimensions that are crucial to its design.
It’s a very useful component in the manufacturing toolbag, but it’s also surrounded by its share of mystery, myth, and pure misunderstanding. Today, we’re going to help cut through the confusing noise, as we tackle some common (and untrue) legends regarding GD&T
Myth 1: GD&T Is Far Too Confusing
You’ll hear this one bandied about by those who are unwilling to take the time to properly understand anything that requires a modicum of effort. “I don’t get GD&T,” they’ll cry, and, to be fair, there is an element of truth to this particular myth. This is a complex standard, and to anyone unfamiliar with what GD&T is, it is going to look like a bunch of nonsense.
Take the time to train, however, with a qualified instructor who has experience relaying difficult concepts to others in a way that simply captures their core, and just about anyone can learn how to untangle the web of GD&T. Again, it’s all a matter of time and effort. Just make sure you don’t fall into the opposite myth here—that you already know all there is to know!
Myth 2: I Can Learn GD&T *SNAP* Like That!
No. While it is true that the rudiments of GD&T can be taught in about two days (roughly 16 hours of training time), this isn’t enough for true mastery. You might know how to read some drawings, for sure, but you still probably won’t know how to make drawings yourself. And you most definitely won’t have the sort of fluency you’ll need to be a true GD&T pro.
That sort of skill comes from dedicated practice. You can expect to put in at least 120 hours of continuous classroom learning, on-the-job training, and practical application before you’re really into the GD&T groove. Don’t fret over putting in the hours, though, as it will ensure that you’re ready for whatever comes your way once you’re using your skills in the field.
Myth 3: GD&T Isn’t Really Necessary
There are some who argue that coordinate dimensioning is all they need. There are even those who believe that GD&T makes production costs skyrocket. Because of factors like this, they say, GD&T isn’t even necessary to learn or implement. The problem with these assumptions is that they are off-the-mark, and the reality is that GD&T is definitely something to consider.
Take the first complaint, for instance, that coordinate dimensioning is sufficient. This neglects all of the advantages GD&T has when it comes to communicating over coordinate dimensioning, and the fact that a significant portion of today’s manufacturers already employ GD&T because it allows for clear rules and the clear conveyance of information.