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.

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.

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

Chinh Nguyen

______________________________________________________________________________________

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.
________________________________________________

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

Our standard title block instructs tolerances on dimensions according to the number of decimal places expressed by that dimension. So, according to our company standard, a 20.00 dimension provides limits of 20.25 / 19.75 but according to para 1.6.1 (b) that is illegal – we should only be saying 20 with no decimal point etc. and stating each tolerance alongside each dimension – something that we would find tiresome and time wasting.

We are very reluctant to have to show the tolerances against every whole number. It seems ironic that for imperial units additional trailing zeros can be used ‘as necessary’ (para 1.6.2(b)).

Can you suggest a legal way around it?

Look forward to your reply / suggestions; thanks for a very useful website.

Robin Davidson

_________________________________________________________________________________

You’re correct. ASME Y14.5 1994 and 2009 both prohibit the use of trailing zeros on metric dimensions and tolerances. So, using title block tolerances that indicate something like this where the tolerance value is based on the number of decimal places is completely inappropriate:

.X        ± .5

.XX      ± .25

This practice for general tolerances originates with the expression of imperial units (inches), but in too many cases has not updated as the company changed from imperial to metric units. The correct method for displaying general tolerances (if you use them at all) for metric units is based on the dimensional value. These can use any interval (range of linear dimensions) imaginable, but one example is shown below. These tolerances are usually listed as a schedule or table near the title block.

0 >   20      ±0.1

20 >   80      ±0.2

80  > 120      ±0.4

120  > 200     ±0.6

I do tend to caution against an over reliance on general tolerances, simply because as general tolerances they are not tied to the functional requirements (failure modes) of each dimension. Considering the maximum allowable tolerance for each dimension may be more work for the designer, but manufacturing and purchasing will appreciate the difference in cost and lead times.

Michael Adcock
ASME GDTP Senior Level
Dimensional Engineering Mentor

If you have a basic understanding of mechanical drawings, we’ll teach you the terms, rules, symbols, and concepts of GD&T as prescribed in the ASME Y14.5M-1994 Standard. You’ll get an in-depth explanation of geometric symbols, including requirements, tolerance zones, and limitations. Read more about the course.

Workshop will be held in ETI’s classroom in Westland, Michigan, 8 miles from the Detroit Metropolitan Airport.
See a map/driving directions.

Read more about the offer here. Call 1-800-886-0909 to register.

In the past, I’ve used basic dimensions for the major and minor axis, a profile control, and a note that says, “TRUE ELLIPSE,” but some metrology labs don’t have the capability to measure ellipses with their CMM.

Answer
Generally speaking, an ellipse is not a true feature of size because it does not have one size dimension that can apply to all opposed surface elements, like a pin, hole, or plate thickness.

You can have two different size dimensions for the major and minor axis, but these size dimensions will not control the surface elements between the major and minor axes. Basic dimensions applied to the opposed surface elements at the two axes and basic radii are best, because then you can specify a profile of surface tolerance applied all around to control the overall size and shape of the ellipse. Datum references can be added to the feature control frame to also control the location and orientation of the ellipse.

Most CMM’s are capable of measuring profile. You can reference the 3D CAD model in lieu of the 2D basic dimensions if the CMM has the capability to measure relative to the 3D model. If a metrology lab is telling you that they don’t have the capability to measure a profile tolerance, then they may be using an older CMM with outdated software or the CMM operator may not have been properly trained on how to correctly measure geometric tolerances.

Roy Cross
ASME GDTP Senior Level S-0488
Dimensional Engineering Mentor

GD&T has been around for about 50 years, yet some people resist using it. What are some of the main reasons you’ve heard from people who are against using GD&T?

If you have any input, I’d love to hear it. You can reply here or join my linkedin group.

- Alex