ETI’s new textbook is here!

Over one year in the making, The Fundamentals of Geometric Dimensioning and Tolerancing Using Critical Thinking Skills is complete and ready for sale.
This third edition of Alex’s GD&T textbook has been completely updated to reflect the changes in the ASME Y14.5-2009 Standard. It preserves the best features of the first two editions while adding new material that reflects the changes in the field of geometric tolerancing.

Our new full-color textbook contains more than 400 pages with new features that aid in the the understanding of geometric tolerancing. It also focuses on critical thinking skills that help the reader when applying newly learned GD&T concepts on the job.

It’s the most practical and easy-to-use GD&T textbook on the market.

Read more about the content, or take a look inside the book.

Order your copy today through our website and receive 20% off the regular price.

Take a look at the large variety of workshops we’re offering this year. We have training based on the ASME  1994 and 2009 dimensioning and tolerancing standards, and we now offer an ISO geometrical tolerancing course, as well.

Click on any link for more detailed information about the course.

• Advanced Concepts of GD&T 2-Day (ASME Y14.5M-1994)
• ASME Y14.5M-1994-ASME Y14.5-2009 Update 1-Day
• Engineering Drawing Requirements 1-Day (ASME Y14.100-2004)
• Fundamentals of GD&T 2-Day (ASME Y14.5M-1994)
• Fundamentals of GD&T 2-Day (ASME Y14.5-2009) – New!
• Fundamentals of GD&T for Inspectors 2-Day (ASME Y14.5M-1994) – Exclusively from ETI
• ISO Geometrical Tolerancing 2-Day (ISO 1101:2004 and related standards) – Exclusively from ETI
• Solid Model Tolerancing 1-Day (Y14.41-2003)
• Statistical Tolerance Stacks 1-Day (Concept Driven) - Exclusively from ETI
• Tolerance Stacks 2-Day (Concept Driven)

ETI public workshops are more in depth than most public seminars, and much more than simply lectures. Each workshop provides hands-on training that includes practice exercises to help reinforce concepts. The price of each public workshop includes materials, continental breakfast, and snacks. Most workshops also include bonus materials, like access to our online training that can be used as a resource after the training is completed.

When you register for any ETI workshop, you know you’ll be receiving the most thorough GD&T training available

The ETI training pyramid shows the hierarchy of GD&T training. Click on the graphic to access a printable pdf of the full pyramid in greater detail.

For more information about workshops and discounts, call 1-800-886-0909, email workshops@etinews.com, or request a quote online.

This is the latest in a series of free resources available on the etinews.com website. Take a look now:

Geometrical Dimensioning and Tolerancing Glossary based on ASME Y14.5-2009

ETI provides a variety of free resources on our website:

• GD&T Skills Survey
• Tolerance Stacks Skills Survey
• GD&T Potential Cost-Saving Calculator
• ETImail: The Online GD&T Newsletter
• The ETI Discussion Board
• GD&T Technical (White) Papers
• Tip of the Month
• GD&T Glossary (ASME Y14.5)
• GD&T Symbols (ASME Y14.5)

The terms in the glossary are from Alex’s 2009 Ultimate GD&T pocket guide, which can be ordered on our website.

The 2009 GD&T pocket guide is spiral bound, so it lays flat. It has several new organizational features, like index tabs, a topical index, and a glossary. We’ve also added references to clauses within the standard and cross-references to other pages within the pocket guide that contain application examples or other related information. Read more about this handy resource.

Be sure to check back often to take advantage of more valuable GD&T resources offered at our website.

The 2009 GD&T pocket guide has 50% more content than the 1994 pocket guide. Its larger format allows room for more charts and graphics, but it still fits in a shirt pocket.

The pocket guide has a glossary, references to the standard, and index tabs on page edges that give easy access to GD&T terms, charts, and drawings.  It’s spiral bound, so it lays flat.

Click the graphic to see a larger view.

The Ultimate GD&T Pocket Guide is a handy reference tool in one convenient pocket-sized package. Carry it with you on the job and have a resource to all your GD&T questions at your fingertips.

This product is a valuable tool for: designers; product, manufacturing, and quality engineers; CMM operators; checkers; quality personnel; engineers; students; and anyone else who uses GD&T on the job.

At only $14.00, The Ultimate GD&T Pocket Guide is a GD&T resource you can’t afford to be without. Order online at our website before June 30, 2011, to take advantage of our June web special.

To read more details and see sample pages, click here.

ETI’s June Web Special: Ultimate GD&T Pocket Guide (ASME Y14.5-2009)
Until midnight EST, June 30, 2011, buy two pocket guides at the regular price of $14.00 each, and receive one free. Sorry, no other discounts apply.

Don’t miss our buy two/get one free special! Order one for each member of your department, today.

Order now.

I put the basic dim +/-.0015 as a tolerance. Engineering requires +/-.003.

Please solve this dilemma.

Adrian

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Adrian,

Your question is both important and common.

Every designer, machinist, and inspector needs to understand the amount of tolerance applied to a part feature. Explaining this is easier if I reference an example, so I have added a figure as a simple illustration of the problem and solution.  I realize that your part is likely much more complex that the figure.

The basic dimensions, such as 5.500, locate the tolerance zone of the position tolerance. The basic dimensions also communicate the ideal location of the hole’s axis. The interpretation is that the hole is to be located at 5.500 from datum plane A +/- 0.0015. The tolerance zone in the figure is perpendicular to datum plane A and any measurements must be made as a distance traveled parallel over the plane of datum A.

Michael Adcock
ASME GDTP Senior Level
Dimensional Engineering Mentor

And be sure to stay an extra day, because the following day we’re offering our one-day Introduction to Statistical Tolerance Stacks workshop.

There are only a few seats left, so don’t delay! Call 1-800-886-0909 or use our online registration form, today.

Course Agenda and Highlights

Can I show them in any vertical or horizontal line as a co-datum A-B?

Thanks,

Yogesh

Hi Yogesh,

It is not clear from the drawing exactly which feature(s) of the part is datum A and which feature(s) is datum B, but from what I can see, you cannot reference these two as co-datum features.

In your example, it looks like datum A is a mounting face that orients the part, and datum B is a feature or features that locate the part. In this case, datum A should be referenced as the primary datum feature and datum B as the secondary datum feature, just like it’s shown in the parallelism callout.

Per ASME Y14.5, two features are referenced as co-datum features when both are required to properly orient and locate the part in its assembly. In other words, one feature by itself is unable to properly orient or locate the part.

A good example of co-datum features is bearing diameters at each end of a shaft. Both are required to orient and locate the shaft in its assembly. Another example is the mounting surfaces of an intake manifold on a V8 engine that are at a 45 degree angles. Both are required to properly orient and locate the manifold on the engine block.

Thanks for your question,

Roy Cross

ASME GDTP Senior Level
Dimensional Engineering Mentor

Chinh Nguyen

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The step-by-step instructions will vary depending upon the CMM software, but the basic requirements come from understanding datum target areas.

In cases where gage blocks or pins are unavailable, or the datum target area is a particularly unique shape, the target area can be simulated by probing the specified area with the stylus. Datum targets (points, lines, or areas) designate only a limited portion of the feature as acceptable for datum simulation, so the key is to produce a tangency from the points taken from this limited area.

Where multiple datum target areas are used to establish a datum (for example A1, A2, and A3), the datum plane must include a high point from each of the target areas.

Here’s an example from our Fundamentals of GD&T (’94) textbook.

Remember, where datum targets are specified there is a specific point,  line, or area from which points can be taken to simulate a datum plane. A common mistake by designers and inspectors is to think that any three points, or any 30mm diameter can be used to simulate the datum. Where targets are indicated, the drawing must specify how the target can be identified (dimensionally) so that part-to-gage repeatability issues do not impact part acceptance.

Michael Adcock
ASME GDTP Senior Level
Dimensional Engineering Mentor

• GD&T Skills Survey
• Tolerance Stacks Skills Survey
• GD&T Potential Cost-Saving Calculator
• ETImail: The Online GD&T Newsletter
• The ETI Discussion Board
• GD&T Technical (White) Papers
• Tip of the Month
• GD&T Glossary (ASME Y14.5)
• GD&T Symbols (ASME Y14.5)

Our newest resource is a glossary of terms and symbols used in ISO geometrical tolerancing. The definitions are from ISO 1101:2004 and its companion published standards.

ISO Geometrical Tolerancing Glossary

The terms in the glossary are from Alex’s ISO guide: Alex Krulikowski’s ISO Geometrical Tolerancing Reference Guide.

The reference guide is used in our ISO Geometrical Tolerancing course, which teaches the ins and outs of utilizing the ISO standards and helps you gain a fundamental knowledge of ISO 1101:2004, related standards, and their application on drawings. Read more about the course.

Please see the attached drawing.

Note: I cannot shift the Datum A since it is a functioning surface.
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ASME Y14.5 permits a few dimensions to be omitted from the drawing because their indication would not clarify the reading of the drawing. Those dimensions are the 90 degree angle, basic 90 degree angle, zero degree angle, and linear dimensions of zero.

Per the drawing you provided, the use of 4X and the composite position tolerance would require the drawing reader to interpret that there are 4 coaxial diameters, even without seeing another drawing view.

The reference to datum A as a primary datum reference requires the reader to interpret that the 4 diameters are to be parallel to datum A, as well as located to datum A within the diameter 0.010 at MMC allowance.

The datum reference to datum B as a secondary datum requires the reader to interpret that the 4 diameters are located 2.675 from datum B within the diameter 0.10 at MMC allowance.

Not being able to see datum feature C in this drawing, I cannot elaborate on the requirement to datum C.

If the rules of ASME Y 14.5 are understood, the reader will understand the relationship to datum A that you were concerned about. This is partly why it is important to evaluate your supplier’s understanding of GD&T.

ETI has some interesting dialogue on this subject on our Linked-in group. Click here to connect with Alex and join the group.

Michael Adcock
ASME GDTP Senior Certified
Dimensional Engineering Mentor