http://gdtseminars.com/blog Geometric Dimensioning & Tolerancing tips, questions and issues Tue, 02 Mar 2010 17:45:29 +0000 http://backend.userland.com/rss092 en Occasionally users of GD&T suggest that everything be simplified by just boiling all 14 symbols down to just two or three.  (What, you didn't know there were 14 symbols?  Click here for a handy chart!)There is some logic to what these people are saying -- namely, that many GD&T symbols overlap others, ... http://gdtseminars.com/blog/2010/03/02/position-and-profile-for-everything/ Another new feature that was introduced in the 2009 standard (ASME Y14.5-2009) is the option of creating a "non-uniform" tolerance zone for either of the two profile symbols.Recall that the profile symbols normally specify a uniform boundary or bandwidth that is centered around the "true" or perfect profile. This true ... http://gdtseminars.com/blog/2010/02/08/non-uniform-profile-tolerancing/ I wrote about this a long time ago, but it's worth mentioning again as the new year approaches (for people who still do New Year's resolutions!).  Regular GD&T users should be aware of the certification process for GD&T Professionals.The American Society of Mechanical Engineers (ASME) has established a credential ... http://gdtseminars.com/blog/2009/12/18/becoming-certified-in-gdt/ OK -- time to dive into another item that is new in the world of geometric tolerancing.  The standard that was released earlier this year expanded the definition of a "feature of size."  This has an impact in that some GD&T symbols can only be applied to "features of size," ... http://gdtseminars.com/blog/2009/11/11/a-new-feature-of-the-2009-gdt-standard/ While everyone is ooohing and aaaahing over the new GD&T standard released in April, there is a rule that dates back to 1994 that very few people know about. And although it's not something that would be used very often, it's something that might be worth filing in the back ... http://gdtseminars.com/blog/2009/10/12/a-little-known-trick-in-the-asme-standard/ Several times I have heard that a designer is hesitant to use GD&T because he knows that the manufacturer will not understand it.  There are several ways to answer this dilemma: Too bad; the burden is on them to learn it Use traditional tolerancing even though it lacks the benefits of GD&T Use ... http://gdtseminars.com/blog/2009/09/21/when-a-supplier-doesnt-understand-gdt/ Out there in the GD&T world, there is often confusion about parts that have irregular shape. We are told that the theory of GD&T requires datums to be 90º to one another. Sure, that's great in a textbook where the examples are nice, rectangular, flat plates!  But what about those ... http://gdtseminars.com/blog/2009/08/20/what-if-datums-are-not-perpendicular/ If you are a regular user of GD&T, you probably know that the ASME standard was recently revised (for details, see the blog entry below dated March 28, 2009).  In today's column, I'd like to introduce you to one of the changes. The term "maximum material condition" or MMC has been ... http://gdtseminars.com/blog/2009/07/30/mmb-a-new-term-in-the-asme-y145-standard/ In a GD&T class, I often talk about (and sketch) how a sample part can be held in a fixture -- this helps people understand the concept of datums, particularly if datum targets are involved. This does not imply that an inspector must use a customized fixture to check ... http://gdtseminars.com/blog/2009/07/01/does-gdt-mandate-that-inspection-use-a-fixture/ Now that the new standard has been released, the demand for training is up!  And while many people simply want to know about the items that were changed or added, each training session is a chance to help folks refresh their memories about the basics of geometric tolerancing. You'd be surprised ... http://gdtseminars.com/blog/2009/05/27/customized-gdt-seminars-bring-your-own-drawings-for-maximum-benefit/