Do I even need datums for this profile?

[ronj100]

My intent is that the profile is good to itself along the designated length. I have added datums to help the inspectors, however, I'm thinking that I can achieve my intent with a profile FCF with no datums at all.
Comments?

 

[CheckerHater]

What "LOCATE" means and how you "locate" your profile wrt cylindrical features of your part?

 

[ronj100]

ignore the LOCATE notes.
They are for the machining center to hold the part.
They are a process note, not a inspection note.
Sorry, I should have removed them for this question or clarifoed that.

 

[CheckerHater]

You ignored the second part of my question.
Nothing in your drawing shows (with or without GD&T) how your profile is related to cylindrical features, which means geometry of your part is not defined yet.
I would also like to mention that GD&T is not created for the sole purpose of inspection, so just because you believe you provided enough information to the inspector, doesn’t mean your GD&T is correct.

 

[ronj100]

Well, i did not mean to ignor your question. The locate notes are for processing and machining. The ends get sawed off and faced after the profile is machined.
The profile IS NOT related to any cylindrical features. It has to be good to itself.
Inspection dept asked for datums in order to inspect the profile. I gave them some datums to locate on. But that concerned me. I did not think it needed datums.
Back to my original question:
The right hand view does not actually need datums, does it? It could just be profile of .003?

 

[3DDave]

These datums make it worse.

Profile is evenly split on each side of the basic shape with the given callout. The nominal distance from the datums to the desired surfaces is zero. This leaves the profile half embedded into the datum simulator, which cannot happen, and is therefore not available for tolerance.

If you excused the wide surface from the profile tolerance and made it flat to .003, keeping datum reference A and ditching B, then you'd have something easier to measure, but without knowing what the part does, it's not possible to say if it's what you need.

 

[ronj100]

Question:
If you remove all the datums and make the FCF profile of .003 (no datums), is that adequate if all one is concerned with is that the shape is good to itself along the noted length within profile of .003?

 

[3DDave]

Datum references are not required for profile tolerance control.

 

[pmarc]

Removing all datum references from the profile callout is okay if one only wants to control form and size of the shape. Choosing some portions of the shape as datum features will indeed make things worse, as 3DDave pointed out.

However, as CH (CheckerHater) noticed, from perspective of part's geometry completeness applying datumless profile callout means that nothing on this drawing controls orientational/locational relationship between the contour and the cylindrical features on both sides of the part, thus the drawing is incomplete.

 

[ronj100]

Thanks. I received my answer.