roughness symbol for raw surface

[cervantes]

Hi

I just got stucked cause I read an opinion of quite experienced engineer and I started to think that I am wrong whole my designing life


See attachment.

Imagine you are buying plate of aluminium, 25x10 and you cut it on saw machine to distance 50.
You do not need to machine length later (you need if you did not follow default tolerance using saw but 25x10 stays raw).
Naturally hole must be machined.

Important: I do not want to specify raw material dimensions somewhere. I only want to use roughness symbols.

So now my question: is APA (any process allowed) - open triangle - clearly defines what I described above as it is shown in attachment?
Or NMR shall be added?... (no material removed on 25x10 - triangle with circle) and then MRR (material removal required) on length?

thanks

 

[KENAT]

I'd avoid trying to specify or even strongly imply manufacturing method unless it's really important to end function or has some other major benefit etc. (ASME Y14.5M-1994 section 1.4e & f).

As memory serves adding the tail to the 'tick' mark for surface finish doesn't change the meaning of the symbol does it?

I'm not sure about your obsession with surface finish for this situation is.

To allow freedom in process I'd just make sure and specify the loosest tolerances I can functionally accept on the actual dimensions (which is what you should normally be doing anyway) and roughest surface finish (if different from drawing default) that is acceptable. I rarely say stock, instead put a loose tol that would allow typical stock variation - exception is on sheet metal where I will often say stock.

Posting guidelines faq731-376

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

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

 

[CheckerHater]

APA will work better, especially if tomorrow you will start using 25X50 stock for some (or no) reason.

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

 

[cervantes]

hmmm

CheckHater, I did some research
in this post:

http://www.eng-tips.com/viewthread.cfm?qid=345230

you've answered like this suggesting NMR (no material removed)

"To designate the surface left in the state from previous manufacturing process use "the circle in the vee" suggested by pmarc.
If you cannot place “no machining” symbol into your title block, leave title block value for machining and create note like “SURFACES IDENTIFIED AS “STOCK” (the circle in the vee)”
You can also attach “machining prohibited” symbol to your “stock” dimension as well."



you see, I revive this discussion once again cause I see a lot of discussion about this on other forums and also on this one
there is no clear interpretation for this symbols for stock surface, in my opinion also in ASME

 

[JNieman]

What you call a stock surface, the previous guy calls a manufactured surface. I assume that's why the symbol does not cover things such as "stock". The broader "material removal prohibited" covers all cases clearly. "Stock surface" is a subjective term which changes depending on the stage of the process. Hot rolled bar sections are made from much larger stock billets, for example.

If you wish, you can do as I do, and dimension the length such as " 25.0 STK " or " 25.0 (STK) " with the 'circle in the vee' symbol reinforcing the restriction from machining where you prohibit.

 

[CheckerHater]

you've answered like this suggesting NMR (no material removed)

In the thread you mentioned, I was answering completely different question.

Also please clarify what do you mean by "there is no clear interpretation for this symbols for stock surface, in my opinion also in ASME"?

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

 

[cervantes]

Ok, sorry for misunderstanding
my question one more time as clear as it can be:

Imagine that I have a symbol obsession and I want to specify raw (stock) material surfaces (they do not need to be machined, it can stay as it is after you bought tchem in shop, like flat bars 25x10) USING ONLY SURFACE SYMBOLS?

Shall it be APA or NMR or something else?...

I just spoke with one of my suppliers (machining company), he replied that their different customers are using both of them to specify raw material on drawings (I mean one customer specifies raw material with APA, other one with NMR).... looks like it allows to interprete your own way

In ASME or ISO there is no sentence how raw material shall be specified. I just read it few minutes ago one more time.

 

[CheckerHater]

Like JNieman mentioned, one man's manufactured surface is another man's "stock".

That's the reason there is no specialized "stock" symbol. Both ASME and ISO promote drawings representing the the function

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of a part, and it doesn't matter what the surface is as long as it works.

You are given symbols for "remove material", "do not remove material", and "doesn't matter". This should cover your basic needs.

Your case is "doesn't matter". If you are using extruded aluminum bar, its surface is probably better than the one after your band saw (or whatever).

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