Nobody sets out to scrap expensive parts, delay production, or end up in a dispute with a supplier.
Most of those problems start much smaller. An ambiguous plus/minus dimension. A note that "kind of" explains the design intent. A feature that never received a geometric tolerance because it didn't seem important at the time.
Collectively, those small decisions cost companies millions.
Small Drawing Errors Become Big Problems
One situation we've seen involved a bolt pattern where a basic angle had been rounded on the drawing. The machine program was created directly from that drawing, and every part matched the program exactly.
The problem wasn't the machining. It was the drawing.
By the time the mistake was discovered, every part had to be scrapped. The cost exceeded a million dollars, all because one value on the drawing communicated the wrong requirement.
It's an extreme example, but it illustrates an important point. Manufacturing can only build what the drawing tells it to build.
Notes Don't Replace GD&T
Another common situation is drawings that rely on pages of notes instead of GD&T callouts.
The engineer knows exactly what they're trying to communicate, and if you read every paragraph carefully. The intent is usually there; the problem is where it's communicated. Inspectors, machinists, and suppliers don't work from paragraphs, they work from the drawing.
Requirements buried in notes are far easier to overlook than requirements communicated directly where the feature appears.
We've seen companies spend years dealing with assembly problems and inspection disagreements simply because profile, position, or another GD&T control was written out in plain English instead of communicated with the symbols designed for that purpose.
If It Isn't Controlled, It Can't Be Rejected
One of the most overlooked consequences of skipping GD&T is that an uncontrolled feature has no geometric acceptance criteria.
If a feature location, orientation, or form isn't specified on the drawing, an inspector has little objective basis for rejecting it. The supplier may deliver exactly what the drawing allows, even if the part doesn't function the way the designer intended.
Leaving something uncontrolled doesn't communicate, "This feature doesn't matter."
It communicates, "This feature has no defined requirement."
The Real Problem
Every example above comes back to the same root cause: the drawing left room for interpretation.
When that happens, everyone fills in the gaps differently. Engineering assumes manufacturing understands the intent. Manufacturing assumes inspection will evaluate the part a certain way. Suppliers interpret the drawing based on their own experience.
Those assumptions usually aren't discovered until parts have already been made. By then, what should have been an engineering discussion becomes a debate over who interpreted the drawing correctly.
That's why good engineers can still produce bad drawings. Long-standing drafting practices, incomplete GD&T knowledge, or simply never being taught a better way to communicate design intent all leave room for interpretation.
GD&T Is the Language of Engineering Drawings
One of the biggest misconceptions about GD&T is that it's all about tighter tolerances.
It isn't.
Everyone works from the same requirements, using the same definitions.
Instead of relying on assumptions, GD&T defines what matters, how features should be controlled, and how parts should be evaluated. Everyone is working from the same requirements before a single part is made.
That's why companies that apply GD&T well spend less time debating drawings, resolving supplier disputes, or troubleshooting assembly issues. The drawing communicates exactly what was intended before a single chip is cut.
The real value of GD&T isn't making parts more precise. It's making drawings impossible to misunderstand.
If your team spends too much time interpreting drawings, debating inspection results, or resolving supplier disagreements…That's exactly what GD&T training is designed to solve.
Start with our free resources, or reach out to talk through what your team actually needs.