Known as the "Doctor of Dimensioning," Alex Krulikowski is a noted educator, author, and expert on Geometric Dimensioning and Tolerancing (GD&T). As a design manager with one of the world's largest manufacturing corporations, he gained more than 30 years of industrial experience putting GD&T to practical use on the shop floor. 

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ETI offers a special deal on a different product each month. Check out this month's Web Special.

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The GD&T Trainer Professional Edition now available!

GD&T Training Made Easy
The GD&T Trainer Professional Edition (Y14.5M-1994) contains 28 student-focused lessons covering the fundamentals of GD&T. Instant lesson feedback and quizzes reinforce the material.

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Highlights include a GD&T glossary, tolerancing application and inspection examples, audio narration, full-color technical animations, 3-D solid part examples, and a certification exam.
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Learn GD&T Fundamentals: Choose from a variety of formats

Video Series Provides Convenient Training
Learn the fundamentals of geometric tolerancing from the design perspective with this step-by-step approach. This 10-tape set can be used as a complete training program or as a supplement to an existing program. Includes a program guide with facilitators' tips and reproducible handouts.

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Video Workbook: Practice GD&T Skills
The video workbook contains diagrams, tips, charts, and key points from the videos. Practice problems and a mini-quiz are also included in each GD&T lesson. The workbook also serves as an excellent reference.

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Learn GD&T At Your Own Pace
Learn GD&T at your own pace, using problems from real life applications. Thirty targeted lessons give you an insider’s grasp of GD&T.

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Teach GD&T Fundamentals: Digital kits put course materials on CD-ROM

 

Digital Instructors' Kits from ETI
ETI now offers all of our instructor's materials in a convenient digital format. GD&T Fundamentals, Advanced Concepts, and Tolerance Stacks Digital Instructor's Kits include everything you need to teach an entire course on one handy CD-ROM.
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GD&T Advanced Concepts taught by the experts. . .

Advanced Concepts of GD&T Textbook
The textbook stresses the application of GD&T in industry and takes an in-depth look at many GD&T topics. Position, profile, and datums are are covered in detail. Covers common industry tolerancing practices not documented in ASME Y14.5M-1994. An indispensable on-the-job reference.
To read more about it, Click here

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Knowledge of stacks separates the exceptional engineers from
the rest

Learn Tolerance Stacks With On-The-Job Focus
Our stacks textbook stresses applications found in actual industrial situations. Solve tolerance stack problems involving flatness, straightness, tolerance of position, runout, concentricity, and more. Practice stacks are from actual drawings and provided in the Drawing Package.

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The "Ultimate" GD&T reference tool is only available thru ETI

Economical Tool You Can't Afford To Miss
Carry this pocket-sized reference with you on the job and have a resource to all your GD&T questions at your fingertips. Includes over 50 detailed drawings, GD&T symbols/modifiers, datum application examples, surface texture, composite tolerancing, conversion charts and more...

At only $5, you can order one for each member of your team!

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ETI Offers On-Site Training 
Effective Training brings hands-on GD&T instruction right to your location. Workshops can be customized to include your drawings and parts.

ASME Y14.41 - 2003
GD&T Fundamentals
Fundamentals Overview
GD&T Advanced Concepts
Tolerance Stacks
ASME-ISO Comparison
Statistical Tolerancing

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ETI's Discussion Board: Talk about GD&T issues with other peers and professionals.

ETI'S Discussion Board
ETI's website has an interactive forum that's easy to access and may give you a broader knowledge of GD&T-related topics. Drop by the Interact section of our website and take a look at the Discussion Board.

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www.etinews.com

ETImail is a regular online publication devoted to Geometric Dimensioning & Tolerancing. Each edition features a host of GD&T resources and links, as well as dimensioning tips by noted GD&T author and ETI founder, Alex Krulikowski. We also invite you to visit our website, etinews.com. To view past issues of ETImail, see the archives.

ETImail is now available in PDF format. To read the PDF file, you will need Adobe Acrobat Reader.

Math-Based Development Processes and Y14.41 Alex Krulikowski The new ASME Y14.41-2003 Standard on Digital Product Definition Data Practices establishes requirements for preparing, organizing and interpreting 3-dimensional digital product images. As chairman of the committee that developed the standard, I am often questioned about its definition, application, and benefits. In this month's article, I'll answer 10 questions about Y14.41.

What is Y14.41?
The official explanation by ASME says:

ASME Y14.41, Digital Product Definition Data Practices, advances the capabilities of ASME Y14.5M, Dimensioning and Tolerancing, the widely used standard pertaining to 2-D engineering drawings. ASME Y14.41 defines the exceptions as well as additional requirements to existing ASME standards for using product definition data or drawings in 3-D digital format.

Representatives from several industries were involved in developing the new ASME Y14.41 standard, including automotive, aircraft, heavy equipment and CAD software manufacturers.

As chairman of the committee, what was most unique about the development process?
The committee developed the standard in six years. Normally, standards are produced over a 10-12 year period. Industry needed this so badly, and technology is changing so fast, we accelerated the standard development to accommodate the needs of industry.

Why is Y14.41 needed in industry?
For over a decade industry has been moving toward tolerancing solid models rather than creating two-dimensional drawings. Prior to ASME Y14.41, there were no standards that covered the display of tolerance information on 3-D models.

There are two important reasons why Y14.41 is critical to industry:

The need to tolerance 3-D models and simplified drawings
ASME Y14.41 advances the capabilities of the Y14.5 Dimensioning and Tolerancing Standard that is used on 2-D engineering drawings. Y14.41 defines the exceptions as well as additional requirements to existing ASME standards for using product definition data or drawings in 3-D digital format. The development of the ASME Y14.41 Standard was initiated at the request of industry and the US Government.

The need to migrate to a math-based product development process
The continuing pressure to bring products to the marketplace in less time and for less cost is requiring many companies to automate their product development processes. Many companies are migrating towards a math-based product development process, which includes four major components:

1. Tolerances are entered once.
This saves labor by eliminating the need for reentry of data. It also eliminates errors from reentry and misinterpretation.
2. Part tolerances are capable of being electronically interpreted.
This eliminates errors from human interpretation of geometric tolerances.
3. The digital data set (a set of model files) is the single source for all information regarding the part.
This allows easy access to up-to-date information and reduces errors.
4. Data is linked and updated automatically.
This saves labor and reduces errors from manually updating information when a change occurs.

These major components result in significant savings in the time it takes to develop products as well as developmental costs.

What the role of standards in a math-based product development process?
Standards play a key role in achieving a math-based product development process. In order to automate the development tasks, the product information needs to be electronically interpretable. Three factors must be met:

• Product information needs to be described in accordance with a single standard.
  
• The standards used must be mathematically robust.
  
• Companies will need to follow national standards and abandon local practices.
  

How important is Y14.41 to a math-based product development process?
Y14.41 is an important standard in migrating towards a math-based product development process. All the efforts I have seen in industry involve eliminating traditional 2-D drawings. Y14.41 documents and standardizes a method used by many companies where a partial drawing is released with a model. It also sets the foundation for eliminating drawings and showing tolerances directly on a model.

How does Y14.41 help communication in an organization?
Engineers, manufacturers, and suppliers can use Y14.41 to communicate model tolerances in a standard way. If two companies show model tolerances differently, the user will have problems finding them on the drawing and knowing how to interpret them. Also, without the new standard, it would be impossible to translate tolerance information from one CAD system to another.

What are the major new concepts in the Y14.41 Standard?
There are too many new features to list here, so I'll highlight a few. The major contribution of the standard is in defining how to display tolerances in a data set, and it does so through two methods:

Method 1: Displaying the tolerances directly on the model. Figure 1 shows an example of displaying tolerances on a solid model.

Figure 1

Method 2: Displaying tolerances on axonometric views of a model in a drawing plus model data set. Figure 2 shows an example of a drawing that shows only the tolerances for the part. The model would contain the basic dimensions.

Figure 2

The standard converts geometric tolerances from a 2-D language into a 3-D language. It defines over thirty terms used in solid modeling. The standard also establishes rules for converting model values to part dimensions.

How does Y14.41 benefit manufacturing?
The new ASME Y14.41 standard can benefit anyone who manufactures parts and uses electronic data. The standard enables manufacturers to implement math-based manufacturing processes. There are many significant savings available to manufacturing organizations if they can automate the design, analysis, and inspection of parts using math-based tools.

How does ASME Y14.41 impact the global economy?
While ASME is a North American organization, its standards are becoming global. Standards have a different role than they did years ago, when they were used primarily in the country in which they were developed. Companies now have plants all over the world, so when a major corporation adopts a standard, the standard is used internationally.

With standards being developed and published in several countries, the challenge is how to harmonize them. Suppliers to major companies often have to work with two or three standards to satisfy their customer requirements. The faster we arrive at one standard, the better it will be for industry. The Y14.41 standard has been submitted to the ISO organization for use in creating an international standard.

What are the major issues facing industry in migrating to a math-based product development system?
There are several tools that need to be improved upon and harmonized for industry to truly achieve a math-based process. I believe these areas need to be addressed to make math-based developmental processes practical on a wide scale:

Standards
The Y14.41 standard is a start, but there is much work to be done nationally and internationally. Harmonization and becoming mathematically robust are two major gaps in standards today. Closer adherence to standards by industry is also an issue that needs to be resolved.

Hardware
Hardware used for CAD is generally too expensive. To have widespread use across all departments in thousands of companies, the hardware needs to be more affordable.

Software
Three areas need to be addressed:

Cost - There is a tremendous difference between CAD software prices. The high-end software packages need to become affordable for smaller companies.
Capability - The software developers need to focus closely on standards. They should encourage customers to use standard specification and discourage customer requests to add features to software that are not compliant with published standards. If this practice continues, it will undermine the standards and hinder the migration to math-based processes.
Complexity - If we are to achieve widespread use of the software, it must be simpler for the user to work in the system. Currently, it can take 6-8 weeks to train a new user. This is not practical for widespread use of the tool.

Translators
The data translators need to be able to translate tolerances in addition to model geometry. Without complete data translation, we will not be able to communicate data across companies. If we had robust translators, companies could work in the system of their choice.

Culture
One of the most important ingredients to change is the culture of the workforce. The math tools can be perfected, but if the culture isn't ready, progress will be slow. Management needs to actively work on developing a culture that embraces and trusts math-based tools. There is a lot of talk about this in industry, but the actions of many management teams do not support cultural change.

How can I gain a better understanding of the new standard?
I recently presented an eight hour seminar on the new standard at the ADDA 45th Annual Technical Conference, in Huntsville, Alabama. ETI is now offering a Solid Model Tolerancing workshop to companies that desire a better understanding of the standard and its application. For more information about the course, click here, or contact ETI at 800-886-0909 to schedule the new onsite workshop.

For information on how to order the ASME Y14.41 Standard, visit the ASME website.

ETImail's Standards in the News takes a look at real-life issues involving standards. This month: a tolerance issue impedes product performance.

Excerpt from the wired.com website

TWIST A PEN, OPEN A LOCK
Standards in the News looks at current issues regarding the use of standards —and the problems that result from their misuse. This issue highlights an article by Leander Kahney in Wired News.

A 50-year-old lock design was rendered useless last week when a brief post to an Internet forum revealed the lock can be popped open with a cheap plastic pen.

On Sunday, bike enthusiast and network security consultant Chris Brennan described opening an expensive Kryptonite bike lock using a ball-point pen. Wired News tested Brennan's claims. A brand new Kryptonite Evolution 2000 was opened in seconds using a Bic pen. After cutting four small slits in the end of the pen's barrel to ease it in, the lock opened with a single twist.

Brennan, 24, of San Francisco, said he successfully opened two Kryptonite locks, an Evolution 2000 and an older Kryptonite Mini lock. Subsequent posts to Bike Forums and other websites report the vulnerability applies to many of the company's cylindrical-lock products, including some from Kryptonite's vaunted New York series.

The New York line carries a $3,500 replacement warranty in the event of theft, and Kryptonite claims the locks are resistant to "bolt cutters, saws, hammers and chisels."

"That's the absurdity of it," Brannan said. "It's not picking the lock or smashing it open. It's the absurdity of a small piece of plastic breaking your unbreakable lock."

Full story

Excerpt is from the article, "Twist a Pen, Open a Lock," by Leander Kahney, in the September 17, 2004, issue of Wired News online. Copyright 2004, Lycos, Inc.

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The ETI Mailbag

Alex,

I am stuck between engineering and quality on the following issue. The drawing shows Datum 'B' , but the problem is that quality and inspection say that the defined datum 'B' is the bottom edge of the part, while the engineer states that design intent is that datum 'B' is defined by
the centerline of the part.

Click on image for larger view.

We have a symmetrical part design in which the design intent is to use a center line as a datum feature. The notation of this datum feature is defined on the extension line of a standard dimension. [1] Is this the correct notation per ASME 14.5M-1994? Or, [2] does the dimension need to be basic so that the datum feature cannot move per tolerances? (Ref. ASME 14.5M-1994 pg. 61 fig. 4-11, 4-13.)

The other suggestion is to simply remove the dimension from the location of the datum identifier so that there is no confusion. [3] How do you perceive this design intent per ASME 14.5M-1994. Also note section 4.3.2 "Datum feature Identification." Your comments and suggestions are greatly appreciated.

Best Regards.

Joe Jackson, Project Leader
De-Icing & Specialty Systems
Goodrich Corporation

Sounds like a lot of confusion going on over how to interpret the drawing specifications. It is amazing how much time can be spent debating tolerance specifications when the drawing isn't clear or the people interpreting the drawing are not skilled in reading tolerances.

There were three questions in your email. The answers are:

Answer 1 - Yes, datum B is specified correctly as the centerplane. On the drawing you submitted, datum B is the centerplane (of the true geometric counterpart) of the 2.75 dimension. In Y14.5, it denotes that when the triangle from a datum feature symbol is in line with a dimension, the datum is derived from the centerplane of the dimension. The 2.75 feature of size is considered the datum feature, and the datum becomes the centerplane (true geometric counterpart) of the feature of size dimension. Since the datum feature is being referenced at RFS, the datum feature simulator would be two parallel planes that contract about the 2.75 width. The center plane of the datum feature simulator is used as the datum.

Answer 2 - I believe you are referring to the 2.75 dimension. This dimension does not have to be basic. (Also, the basic 1.375 dimension is not necessary on this drawing.)

Answer 3 - The figures (4-11, and 4-13) show methods for denoting the center plane as a datum feature and support answer 1.

You didn't ask, but I thought it is worth mentioning: I noticed position tolerance on the elongated holes is specified incorrectly. Consider using the method shown in Y14.5 in figure 5-47.

Best Regards
Alex Krulikowski

I am being asked to inspect true position RFS. The true position tolerance is 0.010". I understand that this is a circular tolerance zone with a diameter of 0.010 with its center at the datum. I measure the dependent feature and find that its centerpoint is 0.006 away from the datum.

Is this part rejectable? What number do I write on my inspection report? Is it the 0.006 distance (while still rejecting the part?), or do I report 0.012 (like the diameter of the 0.006 distance)?

Thank you for your time,

Edward M.

You are correct. The part described should be rejected. I would designate in the inspection report that the tolerance zone allowed was .010 DIA, and the hole location was .012 DIA. Typically, we report the hole location in the same terms as the allowable tolerance zone.

Alex

ASME Y14.3-1994, paragraph 3.2.4 states that the cutting plane should be shown thru an exterior view and not thru a sectional view. Is this a hard and fast rule? On some drawings, taking a section off of a section seems like the best approach for clarity. Your comments?

Thank you,

Paul Reed, Design Checker
General Atomics Aeronautical Systems, Inc.

The practice of cutting a section from a section has seemed to grow in many companies over the last five years. You are correct; it is not in accordance with ASME Y14.3, but it seems to be fairly common in industry. My only thought is to make sure the drawing is clear when using this practice.

Alex Krulikowski

ETI appreciates your questions and comments. Send your GD&T questions to: ETImailbag.

DESIGN, MANUFACTURING AND GAGING ISSUES
This tip is for all the "geotolophiles" out there. (Note: A geotolophile is a person who can't get enough geometric dimensioning and tolerancing.) I found an excellent book on tolerancing — no, not a GD&T book, but a handbook on how to develop optimal tolerance specifications. The book is Tolerance Design: A Handbook for Developing Optimal Specifications. It was written by Clyde M. Creveling, (Prentice Hall PTR, 1996). This is the most extensive work I have found on developing tolerances.

Here is brief excerpt from the preface:

This book covers the three initial phases of the product-development process where tolerance development resides as the final cost-versus-quality balancing process. It explains, in detail, how tolerance design relates to concept design and parameter design. It also relates the tolerance design process to many other engineering and product development tools and tasks, including reliability growth activities.

The book is not for everyone. It is very analytical and includes a number of mathematical formulas used in tolerance development. However, if you are a geotolophile, you will find this book a valuable reference. I highly recommend it.

Tolerance Design: A Handbook for Developing Optimal Specifications is available at various online bookstores. To see a list of a few of them, click here.

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