Square Symbol with Position

[mkcski]

I searched the forum with keyword “square” and found several posts, but none addressed my question. So, I’m presenting the attached PDF for comments.

My question is: How does the position Feature Control Frame (FCF) apply when the square symbol is used. A square is two features-of-size (FOS) – widths (non-circular per Y14.5) at 90 degrees to each other. So, does the square symbol applied to the size “connect” the two widths together and consequently the position control applies to both widths? Or, does the position only apply to the “horizontal” FOS because the FCF only applies to the FOS in the view shown, i.e. there would need to be a second FCF applied to the “vertical” FOS? Or… maybe…is the square symbol an alternative for “2X” and creates a pattern of 2 widths and then the FCF, by default, applies to both (like it would with a pattern of holes with the “X” symbol).


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[dgallup]

I don't think that has any standardized meaning. My guess is that it's implying a square tolerance zone but that is already covered by the lack of a diameter symbol in the tolerance.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[greenimi]

This question has been discussed on linkedin AGI page...there are 43 replies, so quite long discussion....

Applied geometrics GD&T Connection Group


Is this square symbol application to both size of square feature and tolerance zone shape acceptable practice for 1994 Standard (ASME Y14.5M)? And for 2009 Standard (ASME Y14.5)?


One of the most important replies IMHO--see below---but there is way way (5X) more to it.....


Paweł Marczak •
Senior Engineer in Product Definition Engineering, GE Aviation

Of course I don't know that for certain, but my feeling is that the callout shown by Charlie is a result of an attempt of simplifying notation that would be normally/usually used by most people to define the same requirement, that is to use two width dimensions with +/- tolerances and two position feature control frames associated with them. Unfortunately, this ignites several issues:

1. The standard does not support use of the square symbol inside a feature control frame.
2. Some may say that the standard does not provide any details as to how the square/cuboidal tolerance zone should be oriented relative to datums and the toleranced feature (see the thread that Jula gave a link to).
3. Although some may say it is interpretable with the Boundary approach, it becomes muddy when it comes to the Center Plane approach - it is impossible to fit center planes within a tolerance zone that is square/cuboid.

 

[chez311]

Since the square symbol is outside the FCF I would say it does not attempt to describe the shape of the tolerance zone.

The square symbol/notation is not included in Y14.5-2009 section 1.3.42 as a pattern creation mechanism. Since "nX" has specific meaning noted in 1.3.42 as a pattern creation mechanism, to say the square symbol is equivalent would in my mind require specific definition in the body of the standard as to such equivalence. Unfortunately 3.3.16 (as well as Y14.5-2018 section 6.3.16) for the square symbol is extremely limited in its description.

Without further clarification in the standard, I would say the only reliable way to interpret mkcski's original question as well as the notation in Y14.5-2009 section 3.3.16 is that it is a shorthand for individually applying the dimension and associated FCF to each side of the square individually. By this interpretation, unless SEP REQT is specified, these two implied FCF's would be subject to simultaneous requirements - this would create a pattern of features.*

*Edited for clarity

 

[mkcski]

all: Thanks for the responses. I am no longer a member of Linkedin - too many spam and blast messages so I quit

chez311: Your response is where I was headed with an interpretation, especially with the simultaneous requirement for the duplicated FCF. I am also interpreting the tolerance zones to be: a set of parallel planes for the full length of EACH of the two features that are 90 degrees to each other, i.e. not a square tolerance zone at the "center" in the common area where the two sets of parallel planes intersect. I was thinking of presenting something to the committee for the next revision - not sure how to do this - suggestions.

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[chez311]

I am also interpreting the tolerance zones to be: a set of parallel planes for the full length of EACH of the two features that are 90 degrees to each other, i.e. not a square tolerance zone at the "center" in the common area where the two sets of parallel planes intersect.

While the bolded portion would be the correct way to interpret it with the tools that Y14.5 provides us, if the intent is to control the axis which results from the intersection of the 2x UAME center planes of both widths of the square feature then the effect would be the same. If both the center planes of the widths lie within their respective tolerance zones - the axis which is formed by the intersection of these planes will also fall within the shared/common area which is formed by the intersection of these two tolerance zones.

Would what you what you are proposing accomplish something beyond this?

Alternately, the entire square feature itself could be controlled either with profile, or to accommodate expansion/contraction of the profile, dynamic profile per Y14.5-2018 could be utilized. Obviously though this limits variation of each pair of sides relative to each other.

 

[mkcski]

CHEZ311:

I agree with your statement. I am teaching an evening Intro class at a local company and one of the students brought a drawing to me for critique - my sketch was a facsimile of the GDT on the drawing. They are an injection-mold-to-print shop and do not have design information, so they could not answer functional questions. I had never seen this combination of symbols before, and knowing the standard is "silent" on this topic, I "ran" to this forum to see what the collective mind has to offer. Thanks again. Really appreciated!

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