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Unrelated Pattern with Multiple Feature Frames

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GravyBagel

Aerospace
Joined
Sep 30, 2022
Messages
15
Location
US
I am trying to get a series of holes put into a plate. The holes themselves must be reasonably perpendicular to the surface to allow for adequate bolting as they are threaded holes. The translational positions on the plate are not critical and they are not related to each other in any way. I know I could do this with a position call out and +/- dimensions, but I would prefer to use basic dimensions and GD&T to establish circular positional boundaries as opposed to square.

I have my FCF set up as follows:
[tt]
10X Ø0.268 THRU
M8X 1.25 - 6H THRU
|Pos| Ø.2   |B|C|
|Pos| Ø.015 |A|
MINOR DIA
[/tt]
This setup indicates a multiple single-segment FCF though.

Toying with that..
[tt]
|Pos| Ø.2   |A|B|C|
|Pos| Ø.015 |A|
[/tt]
This would indicate that all my hole targets must have the perpendicularity I'm looking for, but also must not vary from each other within 0.015, but the pattern may vary as a whole 0.2.
If I set this up as a composite frame, I actually wouldn't even get the perpendicularity, but the holes would not vary from each other within 0.015 and the pattern would not vary more than 0.2.

Neither of these are really options. I had the idea that if I specified the positional tolerances based off separate datums, I might be able to achieve something different, but I don't think it's the case and I'm running up against the multiple single-segment thing. So I'm not really sure what to do, so I'm hoping someone here can help.

Thanks!
 
You could use perpendicularity with a diametral tolerance zone to control perpendicularity.
 
Thanks for your reply! To my knowledge (limited) a perpendicularity control is equivalent to a position control with a perpendicular datum. This is what I was shooting for with the second line of my fcf. Is this the case or am I mistaken?

It seems that using a perpendicularity control alone will not control the location deviation.
Is there a way to allow the location to float?

Unless you are suggesting position to ABC or BC followed by perpendicularity to A to eliminate the interpretation as a multiple single segment fcf.

Something like…?
[tt]
|Pos| Ø.2 |A|B|C|
|Perp| Ø.015 |A|
[/tt]
Thank you again!
 
Yes - like your "Something like"
 
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