Several Questions About These Position Callouts

[[Da...]]

I have several questions about the position callouts in the attached print. I have no idea how to tell the CMM what I need here. 

 

1) The position callout on the .563 hole (item 3) does not have a datum.

I assume it must be referring to the 1.009 and 2.880 locations from the sides, correct? So I should use those two edges as my datums when I set it up?

 

2) The composite tolerance on the bottom (items 10 and 11) only lists datum A, which is the hole from question 1.

I don't have the CAD model, but I assume if I get it, it will pull in the correct nominals. Wouldn't it need to consider all 3 directions (X, Y, and Z)? I have never done position with more than 2 directions. Is that even possible?

Would I have to do the holes as cylinders? Or would I scan the holes and project them to the faces?

If projecting to the faces, would I use the inner or outer faces since the material thickness could vary?

For the top line, I believe I would have a separate position characteristic for each hole within .030(M), as that is how I would do a regular position. 

For the bottom line, my understanding is that would control the position of each of the 4 holes to each other.

I am confused because I thought the bottom line was supposed to have less datums, but both lines only have datum A. 

If the bottom line is controlling the holes to each other, what does datum A have to do with it?

How do I make the characteristic(s) for the bottom line? Is there a singular characteristic that takes care of the whole pattern or would that need to be separate for each hole as well? 

 

[[Ma...]]

I must admit - this is a confusing one.
I think this is wrong.

TP of datum A is not giving me much sense.
Then TP of 4xø.405 is not giving me much sense in a way how both rows are same, just with different tolerance.

Also datum A is small to have it as proper cylinder and control their location.

For TP of 4xø.405 - .030 tolerance would be pattern and .015 would be individual ones, but i have no experience in composite TP.

I would be glad if main datum would be plane (3.946) and then circle as datum B ( previously datum A )

[[Pa...]]

This drawing is hysterical.  Too bad your sales team opted to accept the job.  Nobody can check this stuff to this drawing.  Datum A has no constraint on any rotations or translations.  It can be in the wrong part in the wrong building in the wrong country and upside down.  True position value is zero.  Perfect every time.

That composite position?  Best I can say is someone in drafting tried pretty hard to engineer but failed.  These four holes can also be anywhere in the world within .03.  The true position value would only be a function of their vector angles to A.  IF the upper FCF had just one additional datum this would make sense.

I'd do the following, but it's not what's drawn:

First probe the hole labeled "A" as a cylinder.  

Now probe the 4 holes as a pattern; I'd go with cylinders.

- Item 3 I'd do as you suggest.  Make the plane through which datum A is bored your primary datum.  I'd make the left edge my secondary and the bottom my tertiary.  I'm making stuff up.  There's no reason you should "know" this, and there is no "correct" evaluation.

-Item 10 I'd use the same primary datum as item 3.  In this case I'd use datum A as secondary.  Again I'm forced to guess what the engineer meant so we'd all interpret this differently.  I'd create a separate position char for each hole.

- Item 11 I'd use only that same primary datum again and ignore the reference to A.  I would not invoke a secondary datum.  Create a position char and select your 4 hole pattern as the feature to be evaluated.

I would communicate all of this to my customer as soon as possible; preferably before you have parts to check.

"position in more than 2 directions": I'm not sure I understand but maybe we're just not using the same words.  Let's try this:

Assuming you've got the old primary plane flat on your table, and the 4 holes are away from you toward Y+,

- the hole labeled datum A has a location in X and Y, with its axis along Z.  Calypso will locate a cylindrical tolerance zone at the nominal X and Y.   When you look at the nominals, the Z value will actually just be the Z value of the feature origin.

- The four holes each have an X and a Z with their axes along Y. When you get your CAD you'll see a nominal X and a nominal Z for each.  Calypso will evaluate deviation from these nominals.

Great questions about projections.  Since your customer did not communicate anywhere near enough information, I would not project these.  I'd check them as cylinders (I'm sure some here will disagree) because I always do.  I've never been comfortable providing positions of projected circles which ignore all deviation to the normal vector.  If some bonehead puts this hole in at 45° rather than 0, a projection won't see it.  Calypso will give a passing true position on a part that will not assemble.

Last thing:  Yes, the bottom line of a composite TP serves to keep the pattern of holes to each other.  It also serves to keep the tolerance zones parallel or perpendicular to datum A.  In this case, if there were a secondary datum in the top line, this bottom line would have smaller (.015) tolerance zones centered around the nominals and perfectly perpendicular to datum A.

Good luck Darci!