• MMS Youtube
  • MMS Facebook
  • MMS Linkedin
  • MMS Twitter
3/1/2007 | 1 MINUTE READ

Decoding (Not Interpreting) GD&T

Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

A suite of online applications aims to help all of the personnel involved with a part to read and apply GD&T information accurately.


Facebook Share Icon LinkedIn Share Icon Twitter Share Icon Share by EMail icon Print Icon

Related Suppliers

Though design, machining and quality personnel all spend considerable time interpreting Geometric Dimensioning and Tolerancing (GD&T) information, Bill Tandler says there shouldn’t be any “interpretation” at all. GD&T is a language for part designs that uses context and symbols to characterize the imperfections allowed in each part feature. In theory, a GD&T callout should carry the same meaning to everyone. In reality, though, the language is complex enough that “tribal understanding” has crept in. Two engineers who work together may not realize they are misreading or misapplying GD&T, because both of them make the same error. When personnel from different tribal understandings come together, however, the result can be a part that doesn’t match the design intent.

Mr. Tandler is the president of Multi Metrics, Inc. (Menlo Park, California). He says that a supply chain could become significantly more efficient if everyone involved had the same ability to decode GD&T information. New products could be introduced more quickly and cheaply, he says, because manufacturing problems resulting from miscommunication could be avoided instead of being discovered on the shop floor. Meanwhile, new suppliers could be brought online more easily, and mid-process design changes could be introduced smoothly throughout the supply chain. Achieving this universal decoding is the goal of his company’s new Web-based utility, “e-GAD.”

The name is short for Electronic GD&T-Aided Design. This suite of online applications aims to guide all of the personnel involved with a part, as needed, through the processes of accurately applying and reading GD&T information. The utility consists of a Best Practices Guide and an Online Advisor. The former is a look-up reference on GD&T, while the latter is a self-guided training resource. Modules ranging from 5 to 30 minutes each use animation and audio to provide instruction in specific GD&T concepts—in effect providing just-in-time training.

Not all tribal knowledge needs to disappear. Mr. Tandler says the utility is password-protected, and therefore can be made unique for each company or supply chain using it. ASME or ISO standards can be followed, for example, and GD&T encoding schemes for a company’s particular part families can be included. In fact, the company’s own part drawings can provide relevant examples, making it that much easier for the user to get to the one correct interpretation of a GD&T callout quickly.

Hand holding a crystal ball

We’d rather send you $15 than rely on our crystal ball…

It’s Capital Spending Survey season and the manufacturing industry is counting on you to participate! Odds are that you received our 5-minute Metalworking survey from Modern Machine Shop in your mail or email. Fill it out and we’ll email you $15 to exchange for your choice of gift card or charitable donation. Are you in the U.S. and not sure you received the survey? Contact us to access it.

Help us inform the industry and everybody benefits.


  • MTConnect Is For Real

    Introduced at IMTS 2008, this communications protocol for CNC machines and other manufacturing equipment is already helping shops and plants implement effective machine monitoring systems. Although these "early adopters" are motivated by the long-term promise of enterprise-wide efficiency gains, their experience with pilot projects shows that benefits derived in the short term are substantial and worthwhile.

  • A Practical Guide To Presetters

    Tool measurement devices help shops save time, control runout and improve tool management.

  • 5 Things New CNC Operators Must Know

    These subjects are the building blocks of training newcomers on a specific CNC machine tool.

Related Topics