Parallelism used in an assembly between two parts 5

[jeff97070]

Can someone help with the question in my subject line.

You have a assembly and you have two parts that you want be Parallel to each other how would you call that out using GT&D Parallelism.

Thank you

 

[CheckerHater]

Thank you both.

 

[MintJulep]

4.7. Installation Assembly Drawing
An installation assembly drawing shows where and how parts and/or assemblies
are installed relative to supporting structure or associated items. It shows
locating dimensions, tolerancing, specifies attaching parts (such as rivets, bolts,
or screws) and specific adjustments, assembly instructions, and processes
required for completing and inspecting the installation.
a. That portion of the structure into which the installation is being installed shall
be shown in phantom and identified by its part number. Such identifications
shall be indicated as reference information by enclosure of the part number in
parentheses or by use of the symbol “REF.”
b. Applicable datum points or planes, such as center lines of structure, plane of
symmetry, station planes, etc., shall be shown and identified.
c. Parts may be detailed in place on installation drawings when convenient.

 

[KENAT]

I suspect some may think of all of these examples as 'special' types of assembly drawings rather than the typical run of the mill sort of assy document and so won't be persuaded.

14.24 doesn't really explicitly say about dimensions for run of the mill assy drawings but does say: "4.1.3 Requirements. An assembly drawing includes as applicable, ... (c) requirements for decorative or protective finishes, processes, settings and adjustments, and other relevant data necessary to complete the item as an assembly...."

So if the parallelism can be achieved by 'processes, settings and adjustments' it seems reasonable to me that you'd directly dimension the required parallelism on the assy drawing.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[fsincox]

We did this all the time with machine tool assemblies that were built "to suit at assembly". I see no inconsistency in its usage at the assembly level. This is another example of how the oversimplification of the standards’ examples tends to work against its application in the field. The datum frameworks are going to tend to be more complicated and may involve using more than just the corner of a single part and the “datums must follow how it is manufactured” group may have trouble. If you look at the assembly as what it needs to function as a whole, I believe, it can be done.
Frank

 

[dtmbiz]

OP’s clarification post:

“Yes two parts that are finished and then shown assembled in a drawing using Parallelism callout between the parts. “

This response indicates an “assembly” drawing.
Basic assembly drawings are a collection of parts which are designed to assemble and disassemble without destruction to the assembly. Certainly it is common and acceptable to apply “reference dimensions’ to an assembly.

Yes, (my earlier post acknowledged) there are different types of drawings that can be types of assemblies.
(e.g. inseparable assemblies, engineering assemblies, layouts, installation, kit drawings, outline, envelope drawings)

And yes, there are manufacturing, test, process, inspection drawings, of which are not assemblies.

Obviously inseparable assemblies are dimensioned with geometric controls as a common practice.
And why not? All of the features function as a single part and those selected features used to define
datums lie within that component. No problem.

My posed question(s) which no one has attempted to address:

“…how can the gage equipment be physically located in the actual assembly?”
“Wouldn't the features that are chosen for a DRF be based on part functionality and mating interfaces?”
Wouldn't those DRF features be inaccessible to gage equipment once the parts are assembled?”

Other inherent problems with tolerance dimensions on drawings:
-Referencing a feature of size given a material condition which is not dimensioned on that assembly.
-Referencing datums with material conditions that are not dimensioned on that assembly
-Referencing datums on one part that are applied to a totally different part

Lifttrucks
A “kit” is not an assembly drawing. It does have multiple components, often those components do not physically touch each other. Commonly used to specify “options” when ordering product or service parts.

It is a “kit” …. “The characteristics of more than one drawing type ….” Not an assembly.

Since you appear to have Y14.24 available, maybe you would share it’s definition of an “assembly” with the participants of this thread.

Ewh,
‘Please, standard number(s) and paragraph(s) to set us straight”

Oh please!
Be glad to, when you provide the standard number(s) and paragraph(s) to set me straight
verifying that 2+2=4. Or how about tolerances for sheet metal gage thicknesses? The standard, not the Machinery Handbook.
Or, maybe you can supply provide the standard number(s) and paragraph(s) to set me straight
from any of the 3 major aerospace engine manufacturers that states you can. All of which I have done or am doing business with. I can’t seem to find those standards.

CH,
I did a job or two with a government agency. That may be a problem you have that I can empathize with. A DOD rocket propulsion company working on concepts for Boeing and Raytheon actually had the entire engineering staff gather together in the auditorium, for me to address the problems that they were experiencing, partly because of combining engineering drawing types. There were over a 100 engineering folks there. Yes, the government agencies will listen to just about anybody. Go figure.

MintJulep,
I have seen NASA standards before. Where in the excerpt that you pasted, indicate that this Installation drawing applies the principles of ASME Y14.5? Really, NASA is going with “symmetry” on a platform installation? ASME Y14.5 (1994 or 2009) symmetry? Would you please explain that to me?

So,
Not one response to address the simple questions that I asked earlier in the post,
in order to have a little professional discussion.

Apologies all, I like to have a little fun with discussion, however this thread has lost any meaningful outcome. As we went thru the thread, my posts tried to distinguish between “run of the mill” assemblies as Kenat calls them, however apparently specific words aren’t working here. My bad.

Believe what you want to; do what you want to; hope it works out for you.

Good enough for me….

 

[CheckerHater]

Dtmbiz,
I have an assembly that I have to check for geometrical tolerance.
What type of drawing according to ASME Y14.24 should I use to document geometrical requirement?

 

[MintJulep]

Ok, I'll continue to play.

My posed question(s) which no one has attempted to address:

“…how can the gage equipment be physically located in the actual assembly?”

That depends on the assembly and the gage equipment that is required. While it is possible to imagine cases where gaging would be difficult or impossible it is also possible to imagine cases where it is quite easy.

“Wouldn't the features that are chosen for a DRF be based on part functionality and mating interfaces?”

It is not necessary that features that require a functional relationship must be mating features.

Wouldn't those DRF features be inaccessible to gage equipment once the parts are assembled?”

Not necessarily.

 

[dtmbiz]

MintJulep

"Dumbutz"?

That's all you have?

Is that German?

 

[CheckerHater]

Well, I pick some.

Referencing a feature of size given a material condition which is not dimensioned on that assembly.
Referencing datums with material conditions that are not dimensioned on that assembly

Ever heard about reference dimensions?

Referencing datums on one part that are applied to a totally different part

What’s wrong with that? I want to position my hand WRT my foot.

Yes, the government agencies will listen to just about anybody. Go figure.

They are required by law to go with the lowest bidder

 

[dtmbiz]

CH,

Really, "required by law"?
Only a naive person would believe that.
Two years ago I was in D.C. for business.
Its not the "law". Its who you know and are connected to
when it comes to many things; especially awarding government contracts.

From my experience, the government pays very well.
After all, its your money.

Naw, in decades of experience I never heard of that term?
Enlighten me.

BTW,
Didn't state "reference dimension".
That is way different than a geometric control callout on an assembly
drawing, which is "referencing" a datum and or feature of size tolerance that exists
on a completely different drawing.

 

[CheckerHater]

Dtmbiz
I was actually talking about reference dimensions rather than “referenced”.
If you look at, say, installation drawings, ALL dimensions on them are “reference”, because the mounting holes were machined long before, per separate drawings.
Nevertheless, Y14.24 suggests using both dimensional and geometrical tolerances on installations.
That creates precedent (since you spend lot of time in court, I figure you’d like the word) – GD&T applied to reference dimensions.
PS
I have no problems to emphasize with. Doing fine in private sector thank you very much.

 

[lifttrucks]

dtmbiz,

You requested that I share the definition of assembly from ASME Y14.24. Here is the definition from Mandatory Appendix I - Definition of Terms:

-----------------
assembly: a number of parts or subassemblies or any combination thereof joined together to perform a specific function, and subject to disassembly without degradation of any of the parts. (Examples: power shovel-front, fan assembly, audio-frequency amplifier.)
-----------------

As far as combination of drawing types, my company uses many subassemblies that included slotted brackets. The drawings include dimensions so the assembler can pre-locate the brackets. Once the subassembly is placed on the assembly, the slots allow for fine-tuning. So this is technically a combination of an assembly and installation drawing. This practice is in accordance with Y14.24.

 

[fsincox]

A ball bearing is really an assembly but they specify all kinds of tolerances for those! Look at the catalogs1
Frank

 

[dtmbiz]

It’s interesting that most are focused on drawing types and what the Y14.5 standard “doesn’t say”.
However that focus does not address application and /or interpretation of geometric controls
shown on an assembly drawing and how to apply the Y14.5 fundamentals to features within an assembly which reside on different parts of that assembly.

Okay, you place geometric controls on an assembly drawing as described by OP.
Explain the details of that parallelism control to the metrology department and to me to please,
as to the criteria for accepting or rejecting assemblies that conform to ASME Y14.5m 1994.

Lift truck
Thank you for posting that definition. It reinforces my previous posted definition.
What you describe that your company uses to” instruct the assembler” is technically a process drawing.

fsincox
You are comparing a catalog sketch / cartoon / envelope / etc. to an assembly?
“A ball bearing is really an assembly…” That would be an inseparable assembly. You don’t distinguish the difference?
The ball, retainer, shield, race, cap, etc. will all have detail drawings to dimensionally define them.
An assembly consisting of drawing views for part relationship and part list information etc. will also exist internally to the bearing manufacturer.

How does your catalog reference relate to an engineering document?

CH,
Sure? I can’t empathize with the problem that your post emphasizes… maybe spelling?

 

[CheckerHater]

I take it you cannot answer my question, so you pick at my spelling.
As classy as obnoxious (did I spell it right?) font.

 

[fsincox]

There are engineering drawings behind the catalogs, at the companies, they will even send them if you request. A bearing is an assembly to the bearing people, you may look at it as a part, but you must see it is really an assembly?
Frank

 

[drawoh]

jeff97070,

I am answering your original question. I see no problems with tolerance and GD&T on assembly drawings, as long as there is some way the assembler can achieve it.

If plate[ ]A is bolted to plate[ ]B, the parallelism will be controlled by the two fabricated parts. There is nothing the assembler can do. At best, the GD&T is for reference, only.

If the connection is adjustable or slotted or whatever, you must provide dimensions and tolerances to the assembler. Hopefully, they will follow your drawings and understand the GD&T. All the standard rules about process and inspection on fabricated parts, apply to your assembly.

--
JHG

 

[dtmbiz]

Sidebar for CH,

I did answer your question the previous post, IMO.
You and others appear not to distinguish between the various drawing types.
Posts continue to ref installations, inseparable assemblies, process drawings, catalog cartoons etc.

From my point of view, since GDT is a language, and the thread participants do not or will not
consider the differences and distinctions of specific terms and definitions... as I wrote
earlier, “…there cannot be any meaningful outcome.” IMO

If there is no difference between assembly; inseparable assembly; installation; process drawing (giving the
"assembler" instructions), then datum, datum feature, datum simulator are all the same because all use
the word "datum".

drawOh just posted and doesn’t see a problem with dimensions on an "assembly" drawing.
Well then the concept of simulating a datum thru the use of gage equipment is out the door.
If the mating production part surfaces which all have been produced at varying tolerances,
and varying form; and those surfaces are used to establish datums... IMO you might as
well just forget about primary Y14.5 concepts. IMO

BTW
Even though I disagree with those that are fine with applying geometric controls to an assembly,
I did not say it couldnt be done, rather that amendments of clarification should be written. IMO

At this point, I could care less if you want to try and apply Y14.5 to your grandma's underwear.
Make up some stinky rationalization... it's your world...

Obnoxious
You actually make me smile. Seriously, you call it obnoxious?
Well was there any insinuation regarding "the lowest bidder"?
I have seen you put barbs in your comments.
"Ever heard about reference dimensions?" your comment CH.
That can be considered "obnoxious".
Are you telling me with the handle "CheckerHater" you aren't obnoxious at times?

You are quite right, I certainly can be obnoxious.
If you're going to dish it out, then prepare for some to come your way.
I do not know you, to banter with you.
I will chill on the obnoxious from my end.

 

[drawoh]

...

drawOh just posted and doesn’t see a problem with dimensions on an "assembly" drawing.
Well then the concept of simulating a datum thru the use of gage equipment is out the door.
If the mating production part surfaces which all have been produced at varying tolerances,
and varying form; and those surfaces are used to establish datums... IMO you might as
well just forget about primary Y14.5 concepts. IMO

I think somebody up above noted that ASME Y14.5 does not mention anything about types of drawings. I agree with this.

You are absolutely right that GD&T controls are futile if there is no way to contact the datums. This is true for assembly drawings, fabrications, service manuals, and any other document you might apply this stuff to.

I routinely design fixtures in which a part is clamped down on top of springs by screws or nuts. The assembler must position the part correctly. My drawing has a note indicating that the dimension units (usually) are in millimeters. A second note states that dimensions and tolerances are as per ASME Y14.5M-1994. Typically, I apply a dimension with tolerances to the appropriate assembly view, e.g. 10[±]0.5.

In ASME Y14.5, plus/minus dimensions are just as valid as feature control frames. The features are accessible to be measured with their digital calipers. I do not think our assemblers understand GD&T, so I am reluctant to use it. I often leave a note on the drawing stating that a 1:1[ ]print is a valid assembly fixture, and I apply a dimension reference that can be checked with a ruler to verify the plot accuracy.

Any reference dimensions on such assembly drawings I mark with brackets, as per the standard.

I also routinely do not indicate anything about the dimensioning and tolerancing standard on my assembly drawings. In this case, any dimensions I apply to the drawings are for reference only. The assembler has no control over them. I have never done it, but I see no reason why I should not apply a feature control frame to show a profile, parallelism or some other tolerance that results from the sufficiently accurate fabricated parts. This could be useful design information. Often, I apply notes to assembly drawings to show ANSI fits such as RC5 or LC5. These things often are useful information, and they function as design notes that explain the tolerances on the fabrication drawings.

--
JHG

 

[dtmbiz]

drawoh

Thank for your post and clarification.
It appears that we are in agreement for the most part.
My view is that the Y14.5 standard is mainly meant to be applied to detail drawings.

Other posts have stated, that Y14.5 does not state Y14.5 cannot be applied to assembly drawings. (Inseparable assemblies are a type of detail drawing)
I find and have experienced problems with geometric controls shown on basic assembly drawings.
The problems come from interpretation of those controls on basic assembly drawings, in lieu of Y14.5 concepts. IMO

Y14.24 defines types of engineering drawings. Often assembly drawings require other useful types of information
as you point out. Y14.5m geometric controls applied to assemblies, without clarification in respect to Y14.5
basic concepts (e.g. simulating a datum) can and does cause unnecessary confusion. IMO


Thanks again for taking your time to post.