before or after plating dimensions

[mechengdude]

Need a little help here. I thought somewhere in a specification it was written that when a part is dimensioned it refers to the part in it's finished state. (ie) if the length is 5.000 +/- .020 and the part is painted then the part must meet this in its final state.

looking in ASME Y 14.5 all I found is that you have to state on your drawing your intent (ie)Section 2.4.1 says use "Dimensional limits apply after plating or Dimensional limits apply before plating"

That basically means that all my drawings need that as we always anodize, paint, passivate, or what ever process is required.

thanks

 

[KENAT]

Sorry what's your question, you seem to have answered it yourself? The standard says to specify if dimensions apply before or after treatment as you say.

I will admit I'm not totally sure on the paint issue, I'd assume the same applies however I can't recall if I actually put that dimensions apply after painting. That said I've almost always applied paint at assembly level and mainly back in the UK.

KENAT, probably the least qualified checker you'll ever meet...

 

[mechengdude]

My question is:
Is there some other specification, standard practice, or similar that states either written or implied that dimension always apply after the finishing process.

thanks

 

[KENAT]

OK, so to clarify is it safe to assume that you work in the US to the ASME/ANSI series of standards?

Assuming this then ASME Y14.5M-1994 is the current standard for dimensioning and tolerancing so pretty much what it says goes. I don't know about earlier versions.

If you don't invoke the ASME/ANSI then it will depend on what you do invoke.

There may be Isos that say different, however back in the UK if we treated the part we normally said dimensions apply after plating (or whatever process).

You could have a company spec that says it.

Arguably standard practices are only really standard practices if they're in some kind of standard. People often talk about 'standard practice in the industry' but upon examination it will turn out that while that may be the most common way to do it in certain geographic or industry areas there are exceptions.

KENAT, probably the least qualified checker you'll ever meet...

 

[CheckerRon]

Some companies use the term "coating" or "finish" as in "Dimensions apply after coating". Thus it covers all, including paint.
I am used to using a note that states dimensions apply AFTER, thus measuring in the final state.
The company I am at now has a standard note that states "Dimensions apply BEFORE finish." The problem with this is that one must keep in mind the effect of coatings on the end product regarding close tolerance fits, and final inspection has account for it too. To me, applying this is before finish is "in process" and only the final part size (drawing dimension) should apply.
Anyone disagree?

 

[Heckler]

This is a revolving topic thread1103-191826

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 4.0 & Pro/E 2001
o
_`\(,_
(_)/ (_)

This post contains no political overtones or undertones for that matter and in no way represents the poster's political agenda.

 

[ctopher]

Notes
1. New thread not to be started unless, thread1103-191826: plating tolerance, has been read.


Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

 

[weavedreamer]

2.4.1 Plated or Coated Parts. Where a part is to be plated or coated, the drawing or referenced document shall specify whether the dimensions are before or after plating. Typical examples of notes are the following:
(a) DIMENSIONAL LIMITS APPLY AFTER PLATING.
(b) DIMENSIONAL LIMITS APPLY BEFORE PLATING.
(For processes other than plating, substitute the appropriate term.)


Stating it helps prevent confusion and ambiguity.

 

[CheckerRon]

Your right Heckler, this subject was beat to death in the thread you referenced. Exceptions are plated threads, class 3 especially, and whether or not you have ME's that do something and cover the in-process stuff. KENAT knows what I am talking about re: ME's.

 

[fcsuper]

That other threat is still open too.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[KENAT]

Checker Ron, you mean MEs that actually do what the classical definition of manufacturing engineering is, rather than being pseudo design engineers!

As fcsuper points out, not quite to death in that other thread.

2 things which I've come to realize:

1. You need to know what the relevant plating spec says as there's a chance it my impact this.

2. For threads, you need to know what the thread spec says. Certainly ASME B1.1 goes into some detail of how finishes apply to threads.


KENAT, probably the least qualified checker you'll ever meet...

 

[BARM]

Weavedreamer,

When I was working in the forging(<5lbs) industy we often were responsible for parts that were plated(outsourced).

On our finalized part drawing that was used by everyone for inpection purposes we applied the following:

Note
1) Part to be plated to spec(XXXXX)
2) All dimensions apply before plating unless otherwise specified.

We would then put the note "BEFORE PLATING (size)" & "AFTER PLATING (size)" under the appropriate dimension. This was 99% of the time a thread spec. All other dimensions had enough tolerance in the orginal process not to be concerned about the extra size plating applied.

You'll need to get an agreement with your customer to this method otherwise extra production gauge costs would be incured for inspection of BEFORE & AFTER specs.

 

[BARM]

OPPS! I meant to reply to Mmechengdude.