I asked this question in my Linkedin group, and I’d like to get some comments from ETI’s website visitors:
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.
One of the revisions in the ASME Y14.5-2009 Standard is related to feature of size. In the new standard, the definition of the term, “feature of size” has been revised to make it a general term that refers to two type of features of size: a regular feature of size and an irregular feature of size.
The chart below shows a comparison between the 1994 and 2009 use of the term.
A comparison chart showing the major revisions between ASME Y14.5 1994 and ASME Y14.5-2009 is available at our website. You can also sign up for an online update class, a public workshop or an onsite workshop.
The latest issue of Mechanical Engineering Magazine features an article discussing whether or not the advantages of model-based definition justify the effort to change engineering, manufacturing, and inspection practices.
“Digital Tolerance,” by Associate Editor Jean Thilmany, includes quotes from Alex as an expert on the ASME Y14.41-2003 Standard on Digital Product Definition Data Practices. Alex served as chairman of the Y14.41 Committee and developed a course on Solid Model Tolerancing that is available as an onsite workshop through ETI.
Engineers and manufacturers can use the standard to communicate model tolerancing in an accepted way, Krulikowski said. “If one company shows model tolerances one way and another company another way, the user doesn’t know how to find them on the drawing, or how to interpret them and read them,” he said.
Read the full article here.
Request information about a workshop.
Q – Can you please explain the meaning of the following tolerance symbol? Which type of standard is this, ASME or ISO?
The profile tolerance does not adhere to either the current ISO or ASME Y14.5 standards. Neither standard permits the word “BILATERAL” in the feature control frame. Also, both standards require that the geometric symbol be placed in the first compartment and the tolerance value in the second compartment, followed by the datum references in the third, fourth, and fifth compartments, if applicable.
Thanks for question,
Q – If a basic dimension does not show a specific tolerance what tolerance should be applied?
A – Basic dimensions by nature are a theoretically exact value; however, the feature(s) of a part they define as ideal or exact do need to have tolerances to permit acceptable levels of imperfection during manufacturing.
When a feature is defined with basic dimensions, the tolerance for that feature must be expressed through a geometric tolerance. Most often, the geometric tolerance is indicated directly to the feature or feature of size on the face of the drawing; however, some companies include a general geometrical tolerance (such as a position tolerance or profile of a surface tolerance) in the drawing’s general notes. This can be an effective tool when the note is carefully written.
Drawings based on ISO standards frequently use a class of general geometrical tolerances standardized in ISO 2768-2 :1989. The three classes are identified through the use of the upper case letters H, K, or L after the ISO 2768 indication on the drawing. You would need a copy of the standard to interpret the amount of tolerance available.
If you are absolutely certain that a geometrical tolerance has not been applied to the basic dimension (check all drawing views), then the drawing must be considered as incomplete. Without a tolerance, selecting a manufacturing process for the considered feature is impossible to do with any amount of certainty, and there is no acceptance criteria to compare measurements to during the inspection process.
Thanks for writing,
A few years ago, I decided to put together some type of graphic that would organize and illustrate the many levels of workshops that ETI offers. It needed to include the prerequisites for each course and some way to easily visualize the entire GD&T training hierarchy. The GD&T Training Pyramid was the result. (Click on the graphic above to access a larger view.)
The pyramid allows you to see all the training levels, as well as the basic courses – or the foundation – upon which your GD&T education should build. We often find that students attempt to master a higher level course without fully understanding the basics. For example, if you don’t completely understand the requirements of engineering drawings, you won’t be ready to learn GD&T fundamentals.
The pyramid also incorporates the valuable concept of mentoring employees. Once a workshop is over, mentoring allows employees to utilize their newly attained GD&T knowledge to its full potential on the job. The gray areas in the pyramid signify those areas where I advise that the mentoring be implemented.
In these tough economic times, companies often cut training budgets first, but allowing ETI to assist them in incorporating a mentoring program into the workplace can often mean valuable dollars are saved through the best use of manpower and materials.
In future blogs, I’ll go into more detail about each of the pyramid’s levels. If you’d like your own copy of the GD&T Training Pyramid, click here.
Here’s a question we received last week…
I have been talking with some drafters and engineers about the standard and have heard varying answers. I’m wondering about when you state the ASME Y14.5-2009 Standard on your drawing in a note or in a title block what it actually means.
Ex. “INTERPRET DIMENSIONING AND TOLERANCING PER STANDARD ASME Y14.5-2009″
Does it mean that the print will always be dimensioned using GD&T?
Does it force you to only dimension using GD&T, or can you use the basic limit dimensioning style?
Does the basic limit dimensioning style still fall under that standard?
Great question! People often wonder if invoking the Y14.5 Standard means that they can no longer use limit dimensions (some call it coordinate tolerancing). The Y14.5 Standard does allow the use of limit dimensions. Also, when specifying the Y14.5 Standard, it invokes Rule #1, which helps to clarify where limit dimensions are used as size dimensions.
However, the Y14.5 Standard discourages the use of limit dimensions for locating features of size (i.e. holes, widths, tabs, etc.).
Using limit dimensions for locating features of size has three major shortcomings:
- The square (or rectangular) tolerance zones are overly restrictive.
- The tolerance zones are always a fixed size.
- There are no specifications for how to hold the part for measurement.
The first two shortcomings result in less tolerance for manufacturing. The third shortcoming of limit dimensioning is that it results in confusion or disputes over inspection results. The lack of datum specifications leaves the drawing with at least several interpretations.
I hope this helps.
Earlier this month, I blogged about my new geometric tolerancing book that explains the use of ISO standards on technical drawings:
Alex Krulikowski’s ISO Geometrical Tolerancing Reference Guide
It’s a comprehensive book that can be used to learn the topic, and it’s also a great reference guide. The book is based on ISO 1101-2004 and companion standards.
ETI is offering a course this fall that utilizes the new book. The ISO Geometrical Tolerancing 3-day workshop will be held September 29th – October 1st, here in the Detroit area. The three-day ISO workshop will help you to understand engineering drawings that use the International Standards Organization (ISO) standards.
The course was written with three goals in mind:
1. To help you recognize what is required on a good (standard-compliant) drawing
2. To help you understand geometrical tolerances based on the ISO standards
3. To combine and explain information from dozens of ISO standards into a logical understandable topic
You’ll learn about …
- ISO drawing conventions
- GPS basics
- Limits and fits
- The datum system
- Form controls
- Orientation controls
- Location controls
- Run-out and profile controls
- General tolerances
- Workpiece edges
- Surface texture
- How ISO compares to ASME
If your company is interested in global sourcing and learning how to read drawings created in other countries, this workshop is vital to your success. It will teach you the ins and outs of utilizing the ISO standards and will give you a fundamental knowledge of ISO 1101:2004, related standards, and their application on drawings.
Those who attend the workshop will receive:
Alex Krulikowski’s ISO Geometrical Tolerancing Reference Guide
- An ISO Geometrical Tolerancing Workbook
- Class handouts
- An official certificate of completion
Read more about the course and specific topics here. I hope to see you in the Detroit area for this exciting new workshop.
The new ASME standard contains numerous changes that affect the specification and interpretation of tolerancing. Companies deciding whether or not to update to the new standard need to understand what has changed and how these changes will impact their product.
As one of the people involved in creating this new version of ASME Y14.5, I have developed a one-day “ASME Y14.5-2009 Update Workshop” that will teach you about the pertinent changes to the standard. This workshop covers over sixty significant revisions, additions, and deletions to the standard. I’ll explain new features and compare them to the 1994 Standard. As part of the course, you’ll receive a set of comprehensive, illustrated charts that highlight itemized changes in the standard.
This drawing shows a small percentage of the changes in the ASME Y14.5 Standard. Click to see the entire drawing.
I’ll explain the major changes to the standard, including:
- Over thirty new or revised terms
- Sixteen new or revised symbols
- Revisions and additions to the fundamental rules
- Revisions and additions to the concept of feature of size
- Revisions and new symbols for datum specifications
- Revisions to composite position tolerances
- Surface boundaries and axis methods of interpretation
- Revisions and new additions to profile tolerances
The ASME Y14.5 1994-2009 Update Course will help you to:
- Understand changes in the standard
- Learn about new symbols and how to apply them to drawings
- Determine the impact of the new standard
ETI can provide this training at your site, and it is also being offered as a public workshop in Michigan on Monday, September 28, 2009. The regular price of this workshop is $375; the first 20 registrants pay only $175.
Attendees must have a basic understanding of Y14.5-1994 Dimensioning and Tolerancing practices.
Each workshop participant receives:
The workshop registration form is available at the ETI website. I hope to see you there!
The new ASME standard contains numerous changes that affect the specification and interpretation of tolerancing. As one of the participants in the creation of the new standard, I will provide insights as to why the changes were made at a lecture on August 13th, from 9 am-12 noon, here in Michigan.
“A Quick Look at the ASME Y14.5-2009 Standard” is a short, 3-hour session about the new ASME Y14.5-2009 Standard. This update session will get you started in understanding the depth of the changes and new features, and it includes a discussion about when it makes sense to implement the new standard. Topics covered include:
- The ASME standards development process
- Introduction to new and revised terms
- Introduction to new and revised symbols
- Synopsis of major changes and why they were made
- Discussion on implementing the new standard
- Questions/answer session
The regular price of this workshop is $50, but the first 20 people to purchase my white paper/comparison chart package for $30 can attend for free.