Reference dimension, Assembly drawing and Y14.5 2009

[Bouing]

In an assembly drawing,

Do you put dimension as REF () or not in an assembly?

In 1.3.24 is clear as what is a reference dimension and it applies to assemblies.

In 1.4o gives an opportunity to leave it without ref but in an assembly this is not a feature but a stack on features.

Most of the assembly drawing I see don't have REF on dimension. It fill the drawing with useless REG or () everywhere except when you localize a part to be fixed (weld, glue, part in slot)

What do you do?
What do you thing you should do?

Robin
Montréal

 

[ewh]

Unless the part is being fabricated to meet those dimensions at that drawing level, the dimensions should be reference. Wherever you have dimensions that are being repeated from component part details, they should be reference.

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]

 

[KENAT]

As per ewh, plus I'd minimize the number of Reference dimension except where they are particularly useful to the user for some reason.

For instance, it can be useful to have some kind of overall ref dimensions to get a feel for the size of the assembly.

However, I just realized you're specific about 2009 which I don't have.

Posting guidelines faq731-376

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

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

 

[CheckerHater]

Your question is "as big as life" with variety of drawings out there.

Say, overall or "envelope" dimensions usually considered not reference, even if they are "self-fulfilling".

Inseparable assemblies are technically assemblies but may contain lot of machining dimensions and be very "part-like".

How about some example?

 

[drawoh]

Bouing,

At the moment, if I feel a need for reference dimensions on my assemblies, I just put them on without the brackets, and without reference to ASME Y14.5. If I need an assembly dimension with tolerances, I reference ASME Y14.5, and I put brackets around any reference dimensions I have provided.

JHG

 

[MintJulep]

An assembly drawing shows how to put two or more components together.

If a dimension is not necessary for that purpose it does not belong on an assembly drawing.

If a dimension cannot be affected by the assembly process it does not belong on an assembly drawing.

 

[ptruitt]

If a 'real' dimension is on a part or subassembly and it is used on more than one higher-level assembly with reference dimensions, do you have a formal policy that everyone follows that says that you must look at all of the higher level assemblies to see if the 'real' dimension has been referenced every time a 'real' dimension changes? I almost never use reference dimensions in order to reduce errors.

Peter Truitt
Minnesota

 

[Bouing]

I put dimensions in the assembly for "others".

Marketing needs overall dimension for selling purpose.

Client needs interface dimension (bolt pattern and thread size) and envelope of product.

Production need overall dimension for packaging purpose.

Welding need plates thicknesses to have an idea of weld power.

In common market drawing we never place those brackets since common people have no clue what it is.

In a welding assembly where it is a placement dimension, it is clear that it is not a reference but mandatory.

I use the same cartridge for every drawing so I don't want to remove the 14.5 marking.

There is no policy to work with, I am self employed and look for what we should do but it doesn't seem to be clear.

If I put no dimension on an assembly, people keep coming to ask questions about dimensions for many reasons.

May be there is another standard covering this?

I think I'll keep using brackets.

 

[KENAT]

Well, no reason you can't keep the brackets/parenthesis and just add a note saying 'DIMENSIONS IN PARENTHESIS ARE REFERENCE ONLY PER ASME Y14.5M-2009' or something like that for users that aren't up to speed on 14.5.

Posting guidelines faq731-376

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

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

 

[ptruitt]

Read "Engineering Documentation Control" by Frank Watts for a comprehensive answer to your questions.

Peter Truitt
Minnesota

 

[ptruitt]

This Standard should also be useful:

Y14.100 - 2004 "Engineering Drawing Practices"

Peter Truitt
Minnesota