Radial Runout Primary Datum evaluation

[[Cl...]]

What is the correct evaluation for the primary Datum used in Radial Runout?

I was under the impression that it was Outer tangential? If I apply
Minimum Feature I get correlation with a roller gage/test indicator.

[[Br...]]

I would always use Outer Tangential for Datum Features.

[[Cl...]]

That's what I've always used too, but I doubted the result from one part and checked it with a roller gage/test indicator.
I wasn't seeing what the CMM was telling me. So I started playing around with the evaluation settings until I got a match.

[[Br...]]

Outer tangential is very susceptible to outliers so you do need to filter when using it, but it best represents the Unrelated Actual Mating envelope necessary to produce the Datum Axis.

[[Da...]]

I take it that you are using a cylinder as the primary datum ?

[[Cl...]]

Yes.

[[To...]]

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aha That is Rule #2 in the "How To Make It Green" training. Rule #1 being "Replace the red ink cartridge with a green one."