In order to fully comprehend much of this overview, it is imperative to have a copy of the 2009 Standard at hand to study the figures referenced in the explanations, which limited space does not permit us to duplicate here. Click on any topic to go there directly and then hit the “Return” button to come back, or simply scroll through the entire article. Overview of the Most Important Changes: The most important changes in the 2009 Standard arepresented in three groups. As we might suspect, however, not everything needing attention can be addressed in a new standard, and there are a few disappointments which also need to be logged. In particular, they will result in significant benefitsfor Tolerance Stack-Up Analysis, for clear communication of manufacturing objectives, and for empowering coordinate metrology software. The many changes contained in Y14.5 2009 represent very useful advances and clarifications which will further empower the designer to fully and reliably express the desired functions of machine parts. In most cases we keep learning as we go, and in the case of GD&T we have learned a lot since 1994. Why do we need a “new” Standard? Standards always represent our bestunderstanding of a topic at the time they are released. Whereas CAD is dedicated to communicating the geometry of a part, GD&T is dedicated to communicating its functional requirements. What is GD&T? GD&T is a symbolic language with which to research, refine andfinally encode the functions of each feature of a machine part by specifying permissible limits of imperfection to guarantee its operation, assemblability, manufacturability and inspectability.

Finally, we provide a brief overview of the contents of this evaluation before we go into detail. Next we ask why a new standard might be interesting. To set the stage, we start with a definition of GD&T as a whole, in order to be sure we are all on the same page. In order to help potential users decide whether or not to adopt it, we attemptto cast some light on its most important novelties. In March 2009 the ASME has released a new Y14.5 standard, the first since 1994, and there is much in it of great interest and benefit. With editorial contributions from Evan Janeshewski and Ron Grube Multi Metrics & SmartGD&T What’s New in the ASME Y14.5 2009 Standard !

Asme y14.5 knurl dimension