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?

Brian Mebruer
Cooper Industries

Y14.5 Question

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:

  1. The square (or rectangular) tolerance zones are overly restrictive.
  2. The tolerance zones are always a fixed size.
  3. 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.

Alex