Should I constrain Roundness to Diameter?

[[Ty...]]

Sorry if this is common knowledge/practice, does it make sense to constrain Roundness to Diameter? If I do this, I could use the roundness plots to also show the size tolerance zone, correct?

[[To...]]

Not sure what you mean by constraining roundness to diameter. Roundness and Diameter are 2 different characteristics. Neither are normally constrained.

The evaluation for Roundness defaults to Minimum Feature or Minimum Zone and Diameter can be LSQ or Outer Tangential, the 2 most common.

Maybe you could load a screenshot of area in question.

[[An...]]

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See attached.

Contribution_25_02_2019.pdf

[[Ty...]]

Sorry, I should have given a little background. I have a part with a large diameter, but it is extremely oblong. I'm not too concerned with the actual roundness measurement, but the plots give the wrong impression. I have attached 2 roundness plots, 1 unconstrained, 1 constrained to size. The unconstrained plot makes it look like the diameter is pinched inward, but in reality, these are the only places the diameter measures within tolerance. If I constrain the roundness plots to size, the black line would be the size nominal and the red lines would act as the size boundaries, correct?

If I'm doing an investigation and am not concerned with GD&T rules, is constraining the better option? The constrained roundness measured 0.4006mm while the unconstrained measured at 0.3985mm, so pretty negligible.


*Sorry, having troubles uploading the plots