basic dimension from profile?

[TWJR]

Hello,

I have an oddly shaped part, in which the outside shape is toleranced by a profile feature control frame. It references the primary, secondary, and tertiary datums (which are all perpendicular to each other) in the normal fashion. My question is this: I have surface at an angle which is perpendicular to the primary datum, but not parallel or perpendicular to any other datums. There are holes on this surface, but in the view normal showing these holes, there is nothing to dimension them from. Since the outside can be traced back to the original 3 datums (because of the profile feature control frame), can I legally place a basic dimension off of a point on this outside shape?

 

[Belanger]

A sketch will help, but based on what I'm reading, yes you can do that if those holes will then have a position tolerance to the same datums as referenced in the outside shape's profile callout.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[TWJR]

While I can't send pictures of the part, I'll cobble something that is similar enough to make the point...

 

[TWJR]

This is a bit crude, but should illustrate what I mean. First time I've attached a file, so hope it goes through...

 

[Belanger]

Well, you would be OK (I presume you're asking about the .962 dim) if the position tolerance of the two holes mentioned some datum in the sideways direction. But the only datums referenced are A and E. Datum A controls the distance of the two holes from the main face, and E controls the perpendicularity of the two holes. No datum is given to control them from a side edge.
Supposing you added datum C to the position tolerance, then yes, the .962 would be OK since it could presumably be calculated back to datum C via the basic profile of the main outline.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[TWJR]

I'm OK with that... hope our backup checker will be. I'm normally the checker here, but I make drawings occasionally, and of course I can't check my own drawings. Well, I could, but my drawings are all perfect, right?