ASME Y14.5-2018 Standard Released!

ASME has just released Y14.5-2018 Dimensioning and Tolerancing Standard.

It replaces ASME Y14.5-2009 version.

Below is a highlight of handful of changes at first glance.

The new standard is much thicker than the previous – 328 pages, a whooping increase in size from 214. An addition of updated figures accounts for this volume increase. Figures have been updated to include model-based application of dimensions and tolerances. The layout of standard has been revised as well – all sections have been renumbered but the order of information hasn’t changed. (phew!)

Removed symbols:

Concentricity, definition and symbol, has been removed

Symmetry, definition and 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.”

New symbols

 “From-To” – for the direction in which a tolerance or other requirement applies. Paragraph 6.3.32

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. Paragraphs 11.10 and 11.11

New or revised definitions

  • The term “theoretical datum feature simulator” was replaced with “true geometric counterpart”. 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”. Paragraph 7.5.
  • 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.

This is not a comprehensive list of changes. For more details see: NONMANDATORY APPENDIX A PRINCIPAL CHANGES AND IMPROVEMENTS.

Revised standard is available for purchase directly from ASME: