Simiultaneous requirements

[Belanger]

For some reason my brain isn't firing on all cylinders this morning, so here's a quick Q ...

See the attached picture. Regarding the two profile tolerances: At first glance it might seem like the part is allowed to tilt into a parallelogram shape. But since the two profile tolerances have common datum references, they are understood to be gaged simultaneously.

The other side of my brain says that they should just use one profile tolerance that uses the all-around symbol.

Any comments? I only ask because it's a pain to get these folks to make any drawing change.

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

http://www.gdtseminars.com

 

[drawoh]

Belanger,

What is datum[ ]C? I will assume this is the bottom mount face, not visible on the view.

An all round profile WRT datums A, B and C is completely meaningful to me. Even with just datum[ ]C, you are defining a tolerance zone. Your maximum angle would be atan(.05/2.5).

What do they want it to look like?

--
JHG

 

[CheckerHater]

Bad thing: the upper-right corner of the part is subject to title-block angle tolerance (unless you specify perpendicularity between [A] and ).
Good thing: the lower-left corner is dimensioned by basic dimensions and controlled by FCFs. It also appears to be straight. This implies basic 90 DEG angle applied to this corner.
The mathematician in me says “good enough”. But not everyone will be convinced.

 

[Belanger]

Yes indeed, datum feature C is the back face.
I agree that all-around profile would be better, but the current callouts seem to be the same thing.

CH, if these profiles are gaged simultaneously, they override the title block tolerance (which is ±1º).

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

http://www.gdtseminars.com

 

[CheckerHater]

What [A] and are for?

 

[pmarc]

There is "2X" in front of each profile callout. If that means all 4 sides of the square are controlled by profile of surface requirements, I say everything is OK. 4 times basic 90 degrees angle and simultaneous requirement apply here. That being said, the outline of the part must fall within two square profile boundaries 2.45 X 2.45 and 2.55 X 2.55 perfectly centered to each other.

 

[Belanger]

Datum features A and B are used to position some other cutouts around there.

Pmarc, that's what I was thinking, but it sure would be more straightforward if they just used one feature control frame and did the all-around symbol!

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

http://www.gdtseminars.com

 

[pmarc]

It sure would, J-P.

 

[bxbzq]

Side question,
Are datum feature A and B center planes or side faces?
If center planes, are the width and height FOS? Do they have LMC and MMC?

 

[Belanger]

In the graphic, the datum feature symbols for A and B are aligned with the dimensions, so the datums are the center planes. Where referenced in other views, they do not have any modifiers (RMB).

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

http://www.gdtseminars.com