Surface Finish - Assy Title Block

[artnmotion]

Scenario: We use one standard Drawing Template for Parts and Assemblies. Surface Finish shows in our Title Block.

Does this imply a Surface Finish of 125 for all components on an Assy Drawing? I think not, but the Customer thinks otherwise :/

Is there a standard that specifies the placement of a Surface Finish Callout on an ASSY Drawing title block?
Or should I just create a New Template for Assy Drawings (removing the callout)?

Thanks.

-Art

 

[MintJulep]

Change '125' to 'N/A' for assemblies.

 

[3DDave]

I think that defaults in title blocks are at best a source of trouble.

They were originally on formats to save the time to hand draw them, but that has not been a consideration for 20 years for most companies. Standard notes, as symbols or copy/paste, or other, allow for ensuring all the factors are considered while allowing inappropriate ones to be removed.

As an example of the trouble fixed titleblock info can cause, in cases where a part needs a smaller overall surface roughness limit there's often a note that overrides the titleblock, which means there are two places to look. One that's immediately obvious and then another that says 'nevermind.'

If there's going to be a surface roughness in the titleblock, have its value be a blank that can be filled in; as MintJulep indicates, on assembly drawings that would be "N/A"

 

[CheckerHater]

Make it N/A, or, if the block is non-editable, draw the line across.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[JNieman]

I left that entry of our title block editable for that reason. It only makes sense for drawings that imply some machining/fabrication is being done, not for sheets that describe assembly - typically. Exceptions exist of course, as some assemblies have a combination...

...but if that doesn't apply, I agree with "N/A" - don't specify a requirement someone has to prove, if you don't mean it.

 

[dgallup]

All the default title block tolerances come from the model. For assemblies, the default surface roughness is ---

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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.

 

[KENAT]

Surface finish should almost certainly be left editable on template and then be struck out or 'NA' (by the way not N/A per ASME Y14.38a-2002) or just left blank when it doesn't apply.

Posting guidelines faq731-376

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

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

 

[KBeitel]

Under the fundamental rules for dimensioning (ASME Y14.5-2009)

1.4(o) Dimensions & tolerances apply at the drawing level that they are specified. A dimension specified for a given feature on one level of drawing (i.e. a detail drawing) is not mandatory for that feature at any other level (i.e. an assembly drawing).

Now surface finishes are not dimensions & tolerances, but they are specified at a detail level for machining drawings. They are not relevant at an assembly level. If an assembly is to be machined (which is rare), the surfaces to be machined should be specified, but at that level, only the surfaces that are specified for machining are subjected to the minimum surface finish outlined in the tolerance block of the drawing format. All other components of the assembly that are detailed at a lower level are exempt from the tolerances outlined in the tolerance block of the drawing format.



Take care & have fun!

Kevin
"Hell, there are no rules here -- we're trying to accomplish something." - Thomas A. Edison

 

[cbrf23]

Another solution if you don't want to edit title blocks is to specify in notes the surface finish requirement does not apply.

@Kevin - I think you may be misinterpreting that section. Please correct me if I'm wrong, as I'm not a certified GDTP or anything, but I've always understood it to mean specifications at a lower level do not carry up. I.e. A surface finish specified as 63ra on a component print would not carry up to the assembly level print. However, all requirements apply to the print they are on. I.e. If 125ra finish is called out on the assembly print, then all surfaces of assembly would need to meet that 125ra finish requirement.


Also, you cannot say the specification doesn't apply just because there is no machining operation.
For example, I can tell you from personal experience engineering processes for assembly via swaging, that as the dies get worn, it very definitely affects the surface finish of the assembled parts.
This is just one of many possible reasons to have a surface finish requirement at the assembly level.

What it really comes down to is this:

don't specify a requirement someone has to prove, if you don't mean it.

How you go about it is up to you, but if it's on the print, it is part of the requirements at that level.

 

[sammcc]

why specify 63 at a lower level then if it doesn't matter?