Is this usage of 2x angularity and parallelism correct? 1

[Oadriusa]

I am little new to GD&T, and haven't used it with a multiplier to indicate instances before, normally I would just mark them independently but due to space issues in this drawing I want to keep it clean and neat.

My question is, am I using it correctly, the intention is to portray that both side edges are identical, I am not sure if the same rules apply to GD&T as they do for normal dimensioning, i.e. using 2X for a dimension that is repeated.

Thanks!

 

[3DDave]

The use of this to create the Datum B reference is not right, though close.

What is needed is the word "INDIVIDUALLY" beneath the Datum symbol and beneath the Feature Control Frame that references "B" .

 

[TheNedgineer]

I would combine all the repetitive 2Xs in one 2X under the DETAIL note and stress out the simmetricity of the part with a centerline (with a cL note) in the main view.

 

[Oadriusa]

The use of this to create the Datum B reference is not right, though close.

What is needed is the word "INDIVIDUALLY" beneath the Datum symbol and beneath the Feature Control Frame that references "B" .

That's interesting, haven't seen the it done like that before. I did some research and found this example "

http://www.dimcax.com/gdt_web/march-01.htm"

which helps explains it a bit. From this I feel the 2X should instead go along the word "INDIVIDUALLY" rather than the feature control frame

So maybe something like this?

Thanks a lot btw, wasn't aware of this at all!

 

[Oadriusa]

I would combine all the repetitive 2Xs in one 2X under the DETAIL note and stress out the simmetricity of the part with a centerline (with a cL note) in the main view.

The part isn't totally symmetrical, which you can probably tell from the the little detail to the left

But the side edge in the view shown is exactly the same, which is why I was wondering if it is even logical to "2X" a dimension as such, maybe I am missing something.

 

[Burunduk]

The INDIVIDUALLY note for the parallelism control doesn't really make any difference because orientation tolerances do not control multiple features as patterns (the tolerance zones do not become related as result of the number of places indication). "Individually" is the default and only option for parallelism anyway. If that was profile you would need the note.

 

[3DDave]

"INDIVIDUALLY" is needed because there are two INDIVIDUAL instances of Datum Feature B. Each face cannot be parallel to both. Write any complaint to the committee concerning not creating a new word to describe this situation.

 

[Burunduk]

Since each of the two instances of datum feature B is "individual" it is clear that the parallelism controls do not reference both of them at once.

 

[3DDave]

B,

Show that in the standard. They have one example that is ambiguous as to the interpretation. Your bailiwick - go forth and take the assault to the committee. I lean towards being explicit and consistent - you feel otherwise.

Perhaps on a different day you would argue the two surfaces established a mid-plane that was the intended target.

 

[Burunduk]

3DDave,
Check the section on profile tolerances. One of the example figures shows how INDIVIDUALLY placed next to an FCF breaks up a pattern to two individual tolerance zones.

 

[3DDave]

That's nice and not applicable. Now show the exact example of individual datum features being individually referenced at individual locations.

It's not my fault the committee fails so badly at creating grouping and group-exclusion rules. CAD makers manage this every day. "These elements are a group" "This element is omitted from the group."

 

[Burunduk]

The reason why it's inapplicable is also why it's not required for the parallelism feature control frame, even if it's used differently in some other example.
It is enough to place it near the datum feature symbol only.
By placing it near the parallelism FCF, consistency will not be gained anyway. In tolerancing, if something can mean more than one thing, it doesn't mean anything.

 

[3DDave]

No - one needs to identify that a feature is certainly referencing a repetition of a datum feature callout. It is consistent wit other examples where a single feature is tied to a single datum feature reference that itself is patterned into independent instances. That's the explanation the user is looking for and the explanation the user will find.

Don't make the reader do more work to figure out what can be explicit.

Now show the exact example of individual datum features being individually referenced at individual locations.

If you believe it ambiguous, take it up with the committee.

 

[Burunduk]

What's inexplicit about the 2X INDIVIDUALLY being applied to the datum feature symbol?
What misinterpretation may result from it not being applied to the parallelism feature control frame?
Contrary, if 2X INDIVIDUALLY is applied to the parallelism callout, it may imply to the user that the note dismantles a pattern that is not there in the first place.
Sure, that's not what the figure with the multiple hole patterns in the section on position suggests, but since it is suggested elsewhere in the standard, that's a good opportunity for being a bit selective in what to copy-paste from the "picture book".

 

[3DDave]

Oh no - the standard has a contradiction. Take it up with the committee.

 

[axym]

Hi All,

I would have to say that Y14.5's use of the INDIVIDUALLY annotation is confusing, because it is used for different purposes in different sections.

In the Profile section, INDIVIDUALLY is used to "un-group" the tolerance zones in a pattern. Unfortunately in the example in 11-28 it is not clear why it ungroups the 2X and not the All Around.

In the Position section, INDIVIDUALLY is used to indicate a repetitive datum feature (so that a different DRF is created for each instance of the datum feature, instead of one DRF based on all of them together). It is then applied to the Position tolerance to allow multiple instances of the tolerance zone without creating a pattern.

I suppose that the common thread is that INDIVIDUALLY means something like "use a different DRF for each feature" in both these applications. Another way to describe it would be that it removes the pattern-creating aspect of the nX multiplier, making it into just a number-of-places modifier.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[Burunduk]

Evan,
I agree that "INDIVIDUALLY" is used differently in different sections of the standard, which makes its meaning somewhat ambiguous.

I suppose that the common thread is that INDIVIDUALLY means something like "use a different DRF for each feature" in both these applications

I'm not sure why you say that this is the common thread, because in the profile section (fig. 11-28) the note applies only to the upper single segment, which is datumless. It only "un-groups", as you say, what is otherwise a pattern of 2 basically connected true profiles.

Another way to describe it would be that it removes the pattern-creating aspect of the nX multiplier, making it into just a number-of-places modifier.

With that I tend to agree, and it is the reason why I said that the note can be omitted from the parallelism feature control frame in the 5 Jul 23 17:33 post (but not from the datum festure symbol for B) there is no pattern to ungroup.
A related question is - would an omission of "INDIVIDUALLY" near the bottom position segment in 10-38 suggest that a pattern of 24 (and not 4!) ⌀3.6 holes, is controlled simultaneously? The multiplier near the callout is 4X, but there is also 6X near the detail name, which I think applies to everything in the detail. This is what made me open
thread1103-509239.