Known as the
"Doctor of Dimensioning," Alex Krulikowski is a noted educator,
author, and expert on Geometric Dimensioning and Tolerancing (GD&T).
A design manager with one of the world's largest manufacturing
corporations, he has more than 30 years of industrial experience
putting GD&T to practical use on the shop floor.
Furniture Makers Turn to GD&T
sure that metal-furniture components assemble easily requires
precision--not just the first time the parts are run, but
for years and years into a program. Read about companies that
have begun to use GD&T symbols on their part drawings
to help ensure that the products will go together as designed.
Brad F. Kuvin looks at GD&T as part of his article
in Metal Forming
read the article, Click
article is in pdf format. To get a free Adobe Acrobat download,
Device Manufacturers Use GD&T
designers of medical devices are faced with demands for smaller,
better, more sophisticated, and more cost-effective products.
This article by Ron Roth explains why GD&T aids in the
successful development of small-diameter tubings.
From the Devicelink.com
read the article, Click
Concepts of GD&T Textbook
The textbook stresses
the applications 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. It discusses several common industry tolerancing practices that
are not documented in ASME Y14.5M-1994. Three chapters are devoted to
tolerancing of non-rigid parts. This book is an indispensable on-the-job
reference. The text has numerous tips, suggestions and practical applications.
To read more about
Trainer Makes Learning Fun
ETI's GD&T Trainer is the perfect solution to your training needs. It's
an entire interactive GD&T fundamentals course on one handy CD-ROM. It's
convenient, portable, and fun.
To read more about it,
To download a demo, Click
Instructor's Kit Goes Digital
its new Digital Instructor's Kit--all the course materials an
instructor needs to teach an entire GD&T course included on
one handy CD-ROM.
To read more
about it, Click
To download a
Offers On-Site Training
brings the most up to date, easiest to understand GD&T instruction in
the industry right into your location. Either Alex or one of his personally
trained instructors will come to your site to conduct a series of three
workshops that add up to a total GD&T education. Workshops can be customized
to include your drawings and parts.
To find out more about what ETI has to offer your
Employment Opportunities Board
a free forum that enables job seekers and employers to meet. If
you're looking for employment in a GD&T-related industry or
you're a company who needs someone with GD&T knowledge, post
your needs here. Click
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. Click on any subject title and you can browse
through GD&T topics, where you may find ideas to spark your own
Board can provide a place for you to find answers to questions,
an exchange of ideas, and a continued discussion of the ever-changing
world of GD&T.
To visit the board, click
Stay up to
date on the latest industry news with the ETI Tech Calendar.
we do that relates to quality is central to quality control,
yet our efforts should be directed to prevention rather than
Mizuno, from Company-Wide Total Quality Control
(Tokyo: Asian Productivity Organization, 1992)
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 a printable PDF
format. To read the PDF file, you will need Adobe
are this issue's highlights. Click on any link to
jump directly to a feature:
Article: The Tao
of Tolerancing, Part I: Nominal Thinking
in the News: Chrysler
combats poor quality standards in parts from suppliers
GD&T terminology; form
controls and feature of size dimensions; CMM "work-arounds"
GyroRemote, a great new teaching
Comments from readers about
Furniture Makers and Medical Device Manufacturers
Concepts Textbook; GD&T Trainer; Digital Instructor's
Training; Employment Opportunities Board; Discussion
Features: Tech Calendar;
Quality Quote of the month
Tao of Tolerancing,
Part I: Nominal Thinking
article covers my experiences, thoughts, and beliefs on tolerancing.
It is based on observing how many organizations around the world
currently handle tolerancing and how I believe tolerancing can
be handled in a far more successful way in industry. I believe
that using the tolerancing methods discussed in this article can
save as much as 30% of part costs.
The first part of this article covers nominal thinking. The second
part covers how to specify datums and dimensional relationships
for all part features and explores the great controversy on how
parts should be dimensioned. The third part of the article covers
how to establish meaningful tolerance values for each dimensional
relationship on a part, and the fourth outlines a plan on how
to lift your organization from Tolerancing Hell to Tolerancing
Heaven. The fifth and final part of this article reviews and summarizes
all of the Tao Tolerancing Principles covered in Parts One through
begin this journey with an explanation of the title of
this article. Tao (pronounced "dou" or "tou") means "the
path" or "the way." Tao is an ancient Chinese religious
belief and contains a philosophical aspect that can be
applied to how we specify tolerances in industry. A tolerance
is simply "the allowable variation for a part feature,"
so this article is an enlightenment of a philosophical
approach to assigning tolerances to part features.
Nominal thinking is where a designer or engineer believes that
if a part design is theoretically correct in its nominal state,
it will work in its produced condition.
Nominal thinking is a simplistic way of looking at a design; it
excludes the effect of the tolerances. Nominal thinking increases
the risk of problems for the customer and in production. Nominal
thinking is often embraced as a timesaving measure or as a convenience
when using CAD models.
The list below shows some of the fallacious thoughts that are
common with nominal thinking:
assembly problems can be avoided by making an assembly of nominally
designed models or drawings (of parts) and verifying they fit together.
assembly problems can be found using nominal models or drawings, but
many interference conditions cannot be found until the effects of
tolerances are analyzed.
We design parts
using solid models in the nominal condition; therefore, the tolerances
are not needed. The tolerances are going to be whatever the process
This is a dangerous
paradigm. What if the tolerances produced from the processes result
in a product that doesn't function as intended?
tolerances will minimize disputes.
tolerances doesn't minimize disputes; it delays the recognition of
problems to after the parts are built. This is the most expensive
time to discover and resolve tolerance issues.
specification is too time consuming.
tolerances early in the design process takes some time, but it saves
valuable time in process planning and problem resolution that can
delay production schedules.
design our parts at nominal for initial prototypes and assign tolerances
before the part is released for production.
will result in several problems. A cost estimate cannot be accurately
achieved until tolerances are specified. Process plans and gaging
plans cannot be done until tolerances are specified. The earlier the
tolerances are specified, the more time you allow for accurate production
planning, tool design, die design, and gage design.
We make a cross-section
layout of our products in the nominal condition to estimate the
space required for the product.
In a design,
the nominal often changes once a tolerance analysis is performed.
A tolerance analysis requires tolerances to be specified. The sooner
the tolerances are specified, the sooner an accurate cross-section
picture can be established.
that helps to avoid falling into the trap of nominal thinking
is, "You can ignore the effects of tolerances, but you
cannot avoid the effects of tolerances." Tolerance will
exist in the produced product even if you don't acknowledge it
in the design stage. If you want the part to function as intended,
the effects of part tolerances should be analyzed in the design
The earlier you understand the impact of tolerances, the more
time you have to deal with any problems the tolerances may present.
Nominal thinking is risky, and will launch you to Tolerancing
Many companies live in "Tolerancing Hell" and suffer needlessly.
Tolerancing Hell is a state of confusion that exists when tolerances
are poorly specified. They can be vague, not in accordance with
standards, or incorrectly specified. Poor tolerance specifications
are often interpreted inconsistently or incorrectly during manufacturing
and inspection, and are often not adhered to in the plant.
When an organization is in Tolerancing Hell, one or more of the
following symptoms are often present:
- Numerous drawing
- Start-up problems
during new product launches
- High warranty costs
- Disputes over drawing
- High manufacturing
To sum it up, huge
amounts of time and money are wasted in the organization.
Many engineers, designers, inspectors, and toolmakers live in Tolerancing
Hell and don't even realize it. These individuals think they are doing
a good job, from their department perspective, but the overall organization
is experiencing significant waste from the misuse of tolerances. There
is a better option: I call it "Tolerancing Heaven." In part four of this
article I will explain "Tolerancing Heaven" and provide a path to achieve
Why Tolerances are Necessary
Life would be simple if the designer or engineer could design parts at
nominal condition and did not have to specify tolerances. However, then
manufacturing would be faced with not knowing how much tolerance was acceptable.
This would lead to two logical paths for manufacturing:
1. Striving to achieve
perfect part features (zero tolerance)
2. Using as
much tolerance as they felt they needed to produce parts economically
If the first path
was chosen, parts could not be manufactured economically. All processes
require some tolerance. Reducing tolerance where it is has no effect on
part function is a waste of time and money. It is not practical to try
to produce parts with no tolerance.
If the second path was chosen, parts could be manufactured economically,
but they probably would not function well. Often the ability for a part
feature to function is limited by the variation that exists in the part
The two primary reasons tolerances are specified are: to protect part
function and to allow for economical production. Tolerances should protect
the function of the product and represent the maximum amount of allowable
variation permissible. Specifying the largest tolerance provides manufacturing
with the maximum flexibility for selecting and maintaining processes.
Tolerance specifications on a part are a critical element of the design.
In industry, some engineers believe that part tolerancing is responsible
for about 80% of the part cost. Part tolerances affect: tooling costs,
manufacturing costs, gaging costs, start-up problems, warranty costs,
and part revisions for the life of the product.
The method used to establish tolerances is really a method for specifying
and managing part variation. Geometric Dimensioning and Tolerancing (GD&T)
is the accepted industrial language used to specify and interpret allowable
part variation. ASME Y14.5 is the most widely used standard for GD&T in
the United States, and in other countries around the world. Tolerances
are most often communicated through the use of a detail drawing.
Need for a Common Tolerancing Method
Which method to use for tolerancing a part is one of the most controversial
subjects in industry. In many companies, tolerancing methods have been
an ongoing debate for years and years. Establishing a common tolerancing
method is much like establishing a common philosophy or religion for everyone
to follow. A common tolerance specification method will benefit the entire
It takes time and effort. It isn't easy, but it can be done, and will
result in huge cost savings. Without a common method for specifying tolerances,
tolerancing hell will exist in the organization. I will close by summarizing
the Tao Tolerancing Principles (TTP) from this part of the article.
TTP #1 - Nominal
thinking will always result in tolerancing hell.
TTP #2 - You
can ignore the effects of tolerances, but you cannot avoid
the effects of tolerances.
TTP #3 - Tolerances
protect part function and allow for economical production.
TTP #4 - A common
tolerance specification method will benefit the entire organization.
issue: Part 2 - A prologue to the System Approach to Component Design.
In this part, two topics are covered: an explanation of the great controversy
over tolerancing methods and an introduction to a logical method for determining
datums and dimensional relationships for part features.
Standards in the News takes a look at real-life issues involving standards.
This month: Chrysler combats poor quality standards in parts from suppliers.
welcome your feedback. Send comments about this article to ETImailbag.
Your opinions will be posted in the next issue.
Story from Automotive
SPELLS OUT VENDOR LIABILITY
- Frustrated by the high failure rate of components it has been buying
and the recalls and service problems they cause, the Chrysler group has
begun requiring suppliers to sign contracts that assign specific financial
responsibility for the cost of recalls and warranty work.
"[The new plan] assigns responsibility and authority. The side benefit
is lower warranty costs and higher quality," said Donald Dees, vice
president of quality.
"One of the first things I saw when I came here is that there was
no process for determining responsibility," Dees said.
"If it was a
manufacturing issue, that was clearly the supplier's fault. And if it
wasn't manufactured to specifications, that also was the supplier. But
who designed the part and who came up with the specifications? That was
the gray area. We would give the supplier the blueprint but never talk
about the details." Full
article was written by Diana T. Kurylko and Robert Sherefkin and
was featured in Automotive News Online -- Autonews.com
/ June 10, 2002
What is the difference
between Virtual Condition, Resultant Condition, vs. Inner Boundary, and
The definitions of these terms, with examples of each, can be found
in ETI's Fundamentals of GD&T textbook, published by Delmar. Click
on the links below to access pages 57 through 61, the pages that cover
this subject. I hope they help you to understand the differences between
the terms. Links
to pages: 57 58 59
particular topic has bothered me for years. I'm finally taking the time
to address it. I know that in your Fundamentals of GD&T textbook you
clearly show that circularity and cylindricity can only be applied to
a surface, not to a feature of size. However, the examples shown in the
standard clearly indicate that these form controls are placed right under
the feature of size dimension (page 163 of the ASME Y14.5-1994 standard).
I always tell my students that the examples are incorrect. What is your
opinion on this?
You pose an interesting question. The method I use in my books is as
follows: where a geometric control is placed beneath the dimension, the
control applies to the dimension (the feature of size); where a geometric
control is directed to a surface, it applies to the surface.
This is a simple
method to help the reader of the drawing figure out what the control applies
to. This is the method used at GM for years. The Y14.5 standard does not
follow that convention. You will see several examples where a geometric
control is placed beneath a dimension and the tolerance applies to the
surface. I would not say the standard is wrong; it is just a little more
confusing when they do not follow a convention. They leave it up to the
reader to figure out what the control applies to, based on the type of
evolution of Y14.5 has resulted in many changes that make it easier for
engineers and designers to optimize the use of GD&T in transforming
functional design requirements into engineering drawings.
I understand some of the enhancements have forced CMM programmers
to develop "work-arounds" when setting up equipment.
For example, we have a great deal of flexibility in establishing
datum reference frames that simulate actual assembly environments
(multiple feature of size datums, composite feature control, etc.).
With the option to define secondary and tertiary datums as features
of size, it may not be possible to establish a CMM datum reference
frame with the traditional plane of reference, axis of alignment,
and origin functions that I am told are customary for CMM set-up.
I would like to
know if this has been discussed in your forum in the past. If so, has
information been exchanged regarding how CMM programmers have dealt with
has been little discussion of CMM "work-arounds" in
ETI Discussion Board; however, it is an excellent topic for
discussion. We recommend that you post your question on the board,
and start a new thread. Hopefully, your question will generate
comments and ideas from other readers regarding this topic.
If you haven't posted any items before, simply click on this
link to begin the Discussion
appreciates your questions and comments.
Send your GD&T questions to: ETImailbag.
teaching ideas to new products that will assist you in training or on the
job, the ETImail Tech Tip will keep you informed about new technology and
ideas. This month's Tech Tip: GyroRemote, a great new teaching tool.
PRODUCT AIDS IN PRESENTATIONS
I find something that aids me in a lecture as much as this product did,
I have to share it with others. The Cordless GyroRemote by Gyration, is
a wonderful new technological tool that gives instructors and presenters
freedom of movement, as well as more precise control of digital presentations
While on the road
recently, I decided to try out the new GyroRemote. I was teaching the
fundamentals of GD&T to a large group, and was using ETI's Digital
Instructor's Kit to teach the 3-day workshop. On the first day,
I used the GyroRemote. Unfortunately, due to technical problems (which
were quickly resolved by Gyration), I was unable to use the product for
the second and third days of the workshop.
I was quickly able
to see the benefits of the GyroRemote. The presentation on day
one was excellent. The number one advantage to using the GyroRemote
is that it allows freedom of movement. I can't stress enough how
wonderful it was to be able to move around the room during my
lecture. Instead of being stuck next to the keyboard and mouse,
forced to be near a desk or podium, I was able to move freely.
I could look at my audience and walk around, even stand at the
back of the room, all the while being able to use the full functions
of the remote. Unlike using a keyboard or mouse, no tabletop or
flat surface is necessary. I had unlimited freedom of movement.
I was also able to utilize many functions that made the
presentation more powerful. The GyroRemote has 6 easily-programmable buttons,
letting you choose from a variety of features:
- Activate highlighter
with a click and drag
- Spotlight a screen
- Hide and reveal
portions of the screen at a time
- Zoom in with the
push of a button
- Program keyboard
commands into the buttons, such as return, enter, alt/tab, and more
- Select from various
pointing devices: pointer, arrow, hand, and more
- Drop any number
of pointers on the digital slide, to point out various concepts at the
- Activate a ticker
tape with a pre-programmed message
- Clear the screen
with the touch of a button
- Bring up an analog
or digital clock
- Activate the countdown
timer for breaks or classroom activities
The benefits to using
this tool during lectures are endless. I highly recommend
the GyroRemote for instructors who use digital imagery in their lectures
and as a companion to our own product, ETI's Digital
It's compact and fits easily in the laptop bag. I liked the GyroRemote
so much, that I not only bought a back up to carry with me on my next
trip, I also decided to add it to ETI's product line. With tech tools
like the Digital Instructor's Kit and the GyroRemote, teaching couldn't
Once you've tried it, you'll be hooked.
To see more about the
GyroRemote, or to order online, click
you know about a new tech tool or an innovative idea that would
our readers, please write us: ETImailbag.
comments about anything you've read in ETImail? ETI will post your
comments here and provide a forum for more discussion about GD&T
writing from Brazil. I'm starting my studies on GD&T and a
coworker gave me your web address. Your page is very interesting
and has much good information. I wish to keep in contact with
you for more information. Regards, Luiz Henrique Marques.
Hi Luiz, Thank you for writing. Glad you like the ETImail; we hope
it will help you with your studies. Did you get a chance to visit the
ETI discussion board? You may find answers to some of your GD&T questions
there. You can also register to ask your own questions and others will
answer them. Here is the direct link: ETI
You can also go there from the first page of the website, under the Interact
section. The link I gave you is to the GD&T section. There is also a section
on the ASME Y14.5 standard. Again, good luck with your GD&T studies. Let
us know if we can be of any help.
would like to hear from you. If you have an opinion about any ETImail
article or feature, please write to our ETImailbag.