angularity question

[AndrewTT]

Per the attached drawing, is the angularity FCF complete? Or, do I need to call the .047 slot width datum C and make the angularity FCF read A, B, C? Please explain what the correct answer is and why. Thank you!

 

[AndrewTT]

I'm going to look at going away from using position for this feature but, to me, the definition of regular FOS includes this feature. If the committee only wanted opposed parallel surfaces to be a regular FOS then why did they put the wording, "opposed parallel elements" in the definition?

1.1.4 Figures - ".....The absence of a figure illustrating the desired application is neither reason to assume inapplicability, nor basis for drawing rejection..."

 

[3DDave]

The opposing elements of cylinders are parallel, even though they are considered a single surface, so there needs to be a recognition of that. For me, opposing means that surface normals are aligned and of opposite sense, although the latest 'irregular feature of size' has extended that to mean the normals of a feature simulator when the feature itself is so incomplete that this isn't the case. But the main characteristic is that a FOS will, in the direction(s) indicated, arrest the motion of the mating part, which edges like this can't do.

Look into 'Y14.5.1 to see the mathematical definition for FOS and you will see that there isn't even theoretical support.