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Prerequisite Knowledge before Learning GD&T

Posted on: Saturday, August 30th, 2008 in: Uncategorized

When I teach a GD&T class, I have to presume that eveyone is “green” about the topic. Even if some folks have been using GD&T regularly, I find it best to start from the beginning. This ensures that everyone is on the same page, and it sets the stage for presenting the various GD&T topics […]

Roadblocks to Effective Training

Posted on: Tuesday, June 17th, 2008 in: Uncategorized

Nobody has to tell you that training is a valuable tool to help improve your skills and that of an entire group. But so often, a desire to implement training is thwarted by roadblocks. These roadblocks come in different forms. Here are a few, and ways to avoid or work around them:
  

“We don’t have time.” […]

Title Block Tolerances and GD&T

Posted on: Tuesday, May 13th, 2008 in: Uncategorized

In the geometric tolerancing system, basic dimensions are used to override general tolerances (sometimes called title block tolerances). But let’s investigate these general tolerances a little more closely. A sample tolerance block is shown below, as taken from a drawing using metric (millimeters). First, notice that the tolerance allowed depends on the number of digits […]

History of GD&T

Posted on: Tuesday, March 25th, 2008 in: Uncategorized

Instead of discussing some technical point this time, let’s take a brief look back at the history of GD&T. Some people may think that GD&T is “just the latest fad” (I actually heard someone refer to it that way) and therefore they are implying that it’s not worth learning, since it may soon go away. […]

GD&T Instructor Wins SAE Award

Posted on: Monday, February 25th, 2008 in: Uncategorized

SAE International (the Society of Automotive Engineers) has recently announced its winners for this year’s awards, and among them is John-Paul Belanger, from Geometric Learning Systems. Mr. Belanger is receiving the Forest R. McFarland Award for outstanding contributions toward the work of the SAE Engineering Meetings Board in the planning, development, and dissemination of technical […]

The Mysterious Plus/Plus Tolerance

Posted on: Saturday, January 26th, 2008 in: Uncategorized

Here’s an interesting tolerance question: Have you ever seen a plus/plus tolerance? (or minus/minus?) The ASME standard does not mention this, so a purist would say that it is illegal (see paragraphs 2.2 and 2.3 of the Y14.5 standard). But I’ve seen examples such as a hole dimensioned with:
   
The real problem is that, with a casual glance, you […]