Prints shouldn’t leave room for interpretation, and that’s how we approach them at Wagner Machine. Our precision machine shop treats your prints with the same seriousness as a legal document. With that in mind, every dimension matters, all GD&T callouts get reviewed, and if something looks ambiguous, we’re going to ask about it.
Some customers find this refreshing. Others wonder if we know what we’re doing. But those questions are what separate us from shops that assume “close enough” will work. Getting this level of clarity upfront is how we guarantee your parts perform exactly as designed.
Why GD&T Has Become Standard
GD&T (short for Geometric Dimensioning and Tolerancing) has been around since 1973, but it took decades before it was commonly used. GD&T appeared more complex than conventional dimensioning, as it used additional symbols and callouts that required training to interpret. As such, many engineers avoided it and machinists weren’t upset about that.
In our shop, we’ve seen that change significantly over the past decade. GD&T callouts have become widely used in manufacturing because they do a better job of communicating design intent. Instead of treating dimensions as isolated requirements, GD&T explains how features relate to each other and better communicates the functionality of a part.
With true position tolerancing, for example, a hole’s size and location aren’t independent; instead, they work together to ensure proper fit with a mating part. When using the maximum material condition modifier, as hole size increases, the location tolerance increases. Conventional dimensioning doesn’t capture that relationship, which means parts can technically meet spec and still not assemble properly.
When used correctly, GD&T gives manufacturers more flexibility while ensuring parts function as designed. The challenge is that it can be easy to make tolerances tighter than necessary by using GD&T incorrectly, causing costs to rise without adding value. That’s why choosing a partner who understands GD&T and builds that knowledge into their precision machining services, makes all the difference.
If We Machine It, We Inspect It
If a tolerance is on the print, we need to be able to prove the part meets it. Not all shops operate that way, but it’s non-negotiable at Wagner Machine. We won’t machine to a tolerance unless we can inspect it with the right equipment and verify it’s within spec.
That principle applies to every feature, whether it’s a hole location, a profile tolerance, or any other GD&T callout. If we can’t measure it, we can’t guarantee it, and we won’t take that chance.
Tapped holes are a good example of features that are often over dimensioned. We often see prints with GD&T callouts that have extremely tight location tolerances, sometimes down to a few thousandths of an inch, for tapped holes. Measuring those consistently is difficult, and that verification can add cost without improving functionality. A tight clearance hole fit for a bolt has at least .008” or .02mm clearance, so over-constraining the tapped hole location is a cost driver without a benefit. When we see that kind of callout, we always double check with the customer to see if it is a mistake.
It’s not about second-guessing the design, but about making sure we can deliver exactly what the print requires and prove it at a reasonable cost. In many cases, those conversations not only save our customers time and cost, but also help you get more competitive quotes from any shop you work with in the future.
Common GD&T Challenges
GD&T is a valuable tool, but certain applications can unintentionally add cost and confusion, such as:
- Overly tight true position or profile tolerances: A true position or profile tolerance of .005″ is tighter than many realize. That’s roughly equivalent to ±.002″ in conventional dimensioning. On features like tapped holes or an o-ring groove location, that kind of spec can add significant time and cost without improving function by requiring frequent CMM inspections. For many years, +/-.005” has been considered standard for machined features, but the equivalent true position or profile tolerance is .010”, not .005”.
- Non-critical callouts add cost: Additional GD&T requirements on non-critical features may not add value but still require time to inspect and verify. That inspection effort can drive up cost and shift focus away from verifying the features that matter most.
- Follow the rules: It is critical to use best practices to define datums. Tapped holes, short edges, or unstable features are generally bad alignment features to use as datums. Using bad features, or using datums that are concentrated in a very small area of your overall part can cause inconsistent part alignment resulting in poor inspection repeatability even if the parts are consistent.
Our goal is always the same: to support your print exactly as written, while helping you avoid tolerances and callouts that don’t improve performance.
Getting GD&T Callouts Right
GD&T can communicate design intent more clearly than conventional dimensioning, and in many cases, provides manufacturers with the flexibility to deliver functional parts without unnecessary cost.
At Wagner Machine, our priority is to respect your print, eliminate assumptions, and ensure every tolerance is achievable and verifiable. That means asking questions, clarifying gray areas, and focusing inspection where it matters most. The result is precision machining services you can count on, and parts that perform exactly as designed.
Ready to work with a precision machine shop that takes your prints seriously? Request a quote from Wagner Machine today.