Tolerance Interpretation

[[To...]]

I recently had someone ask me how Calypso handles plus/minus tolerances. Many drawings have a legend where general tolerances are designated. In the US, the tolerances are typically established by the number of decimal places of the nominal feature. For example, it would be common to see the following:

.X = ±.030
.XX = ±.010
.XXX = ±.005
.XXXX = ±.0005

Let's assume we have a .50 diameter hole and it measures .514. According to the legend, because this is a 2 place decimal, the tolerance would be ±.010. The above customer says the report is set to show 2 places but the result is red.

Here's where the argument comes into play. Some, if not most, people would say this hole is out of tolerance because .514 is greater than the .010 allowable tolerance. However, others would say the tolerance should be evaluated to 2 places, as well, meaning this hole was good. They claim if the engineer wanted the tolerance to be held tighter, they would have specified it.

What do you think?

[[DW...]]

I report one more decimal place than the nominal as shown on the drawing. So if it is 0.50 inch, I report to the thousandths place. If it was 0.500 inch, I would report to the ten thousandths place. If the diameter measures 0.514 inches, it is not in tolerance.

I have not read this anywhere specifically, but it helps avoid a situation as you describe.

[[Ma...]]

ASME Y14.5M-1994 2.4 Interpretation of Limits

"All limits are absolute. Dimensional limits, regardless of the number of decimal places, a re used as if they were continued with zeros....the measured value is compared directly with the specified value and any deviation outside the specified limiting value signifies nonconformance with the limits."

[[Jo...]]

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