After nearly a decade, the updated ASME Dimensioning and Tolerancing Standard has been updated with essential additions, omissions, and examples to ensure your GD&T best-practices are up-to-date. So what are all the differences you should keep in mind when comparing ASME Y14.5-2009 vs. ASME Y14.5-2018? Our Quality Manager and Certified AUKOM instructor at Made to Measure, Jacek Macias, holds an ASME 2009 Senior Certificate, and helps highlight a handful of the most important changes below.
ASME Y14.5-2018 Dimensioning and Tolerancing Standard Replaces ASME Y14.5-2009
The new ASME Y14.5-2018 Standard is much thicker, weighing in at 328 pages – much more substantial than the previous 214-page 2009 Y14.5 Standard. However, not all of the updated regulations account for the overall increase in size. Figures have been updated to include model-based application of dimensions and tolerances to help contextualize the definitions and conceptualize how they fit into your workday. The layout of standard has been revised as well – all sections have been renumbered, but the order of information hasn’t changed.
ASME Y14.5 Updates: Removed GD&T Symbols
As precision measuring equipment like coordinate measuring machines and non-contact laser scanners are able to more effectively create 3D maps of workpieces, tools, and more, certain context-dependent definitions became obsolete. Because Concentricity and Symmetry are not necessarily concrete values, per se, they have been effectively replaced by measurements with more reliable repeatability.
Concentricity, both the definition and the symbol, has been removed
Symmetry, both the definition and the symbol, has been removed
“Two past practices, use of concentricity and use of symmetry, have been eliminated because other characteristics provide more direct control of features and establish requirements that have a well-defined meaning. Deletion of the symbols does not leave industry without a means to control coaxial or symmetrical features, but it does eliminate the confusion that surrounds these symbols and their misapplication.”
In short, Concentricity and Symmetry were not adequate metrics to produce reliable and repeatable measurements. Furthermore, there are redundant modes of measurement that will still allow manufacturers to constrain symmetry and concentricity with less chance of miscommunication between engineers, draftsmen, machinists, and other essential team members.
ASME Y14.5 Updates: New Symbols Added to ASME Y14.5-2018
Updates to the ASME Y14.5 standard aren’t only relegated to omission. In fact, there are two wholly-new symbols and accompanying definitions you’ll be seeing from now on.
“From-To” – for the direction in which a tolerance or other requirement applies. This symbol is defined and explained in paragraph 6.3.32 in the new ASME Y14.5 manual.
A “dynamic profile tolerance zone modifier” is new, for use with profile tolerancing. The function of the dynamic profile is to allow form to be controlled independent of size. Dynamic profile tolerance zone modifier examples, definition, and more can be found in paragraphs 11.10 and 11.11 in the updated ASME Y14.5-2018 handbook.
ASME Y14.5 Updates: New and Revised Definitions
- The term “theoretical datum feature simulator” was replaced with “true geometric counterpart,” as seen in paragraph 7.5. Types of True Geometric Counterparts – expanded from “an actual mating envelope” to “a related AME” and “an unrelated AME”. Similarly, “a minimum material envelope” has been changed to “a related minimum material envelope” and “an unrelated minimum material envelope”.
- Unequally disposed profile tolerance may only be indicated with U symbol. The use of phantom lines to specify unequally disposed profile tolerance as an alternate practice has been removed.
- Runout Tolerance may be applied to a tangent plane for one or more coplanar feature faces that are perpendicular to an axis of rotation.
Keep in mind that this is not a fully-comprehensive list of changes between ASME Y14.5-2009 and ASME Y14.5-2018.
Made to Measure Can Train Your Team on ASME Y14.5-2018 Updates
If you and your team need help better understanding all the changes between ASME Y14.5-2009 and ASME Y14.5-2018, don’t hesitate to contact our team at Made to Measure. Our ISO 17025 Certified independent metrology lab offers so much more than the most accurate measurements with the latest in CMM technology. We offer GD&T courses, blueprint reading classes, AUKOM certification, and more to ensure that your team has the skills needed to keep tolerances tight and teamwork tighter. Request a quote today to see how and when we train your staff on ASME Y14.5-2018 Standards.
The revised standard is available for purchase directly from ASME.