Another Unknown GD&T Symbol - Enclosed ' V '

[resjsu]

Hello All,
I have come across another symbol I am not familiar with and have not been able to find in any GD&T book. I am starting to lean towards "typo" but the drawing comes from a very prominent Automotive customer and I feel like they wouldnt make mistakes too often. So before I put my foot in my mouth I am trying all other options before I submit a request to have the customer review this specific block of information.

If you look at the attachment the bubble in question is bubble #41, datum B with the enclosed "V." I have not been able to find this circled 'V' anywhere. I am thinking it may be a MMC symbol with the "legs" of the 'M' somehow cutoff but the drawing we have is pretty clear, good graphics, so its not like there is a smudge on it or anything.

Anyways, any help would be greatly appreciated.

Thank you

 

[ctopher]

The dwg looks to me to not follow any drafting practices.
I have never seen "V" in GD&T like this. Just a guess..."vertical"?

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[KENAT]

Elsewhere on the drawing, is there a note referencing their internal drawing standard manual or similar? V for virtual condition maybe?

Posting guidelines faq731-376

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

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

 

[resjsu]

Ctopher: For the most part, the rest of the drawing is defined through GD&T standards.

KENAT: There are no other notes on the drawing regarding internal drawing standards. Virtual condition is a good guess, I will look a little more clsoer at it but my gut tells me it is not for virtual condition.

Thanks for the feedback!

 

[ctopher]

I meant general drafting/drawing standards, not GD&T standards.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[tbuelna]

resju-

Attached is a list of current ASME Y14.5-2009 modifying symbols, and there is no "V" listed. If your drawing has a notation somewhere stating something like "interpret dimensions and tolerances per ASME Y14.5-2009" then the list of modifying symbols applies. The only exception would be if there is some additional instruction provided on the engineering document that describes how to interpret that "V" symbol.

 

[RolMec]

When loking closer, seems to me that those circled V's were added later on. So it could be a (V)ariation from a previous drawing --> Do you have any revision overviews / revision lists to this drawing or perhaps older revisions?
Else, if you have other drawings of the same batch, could you look at those for this symbol? (V)erification would be another guess, then. Perhaps somebody being inventive? You wrote "For the most part, the rest of the drawing is ..", how much is most part?
Regards
R.

 

[Metalfixer]

I'm guessing that it has some reference to a countersink on the holes.

 

[hydtools]

It is time to ask the customer.

Ted

 

[resjsu]

RoleMec: I will definitely look into your ideas. As far as it being a variation form a previous drawing, the drawing has a standard revision block with dates/changes made etc. The current revision level is 'J'. There are not notes on the titleblock referring to this circled 'V'. Yes, for the most part the rest of the drawing is in GD&T; The reason I say this is because if you saw my thread a couple days ago, I posted an image of what turned out to be a very old surface finish symbol, an italic 'f', that I had never seen before but is called out several times on this drawing. I have attached an image of this symbol as well. I was assuming the original drawing was very old but it turns out the original drawing date is 1992 at which time the surface finish symbol was already outdated.

Metalfixer: I will double check but I do not think so.

hydtools: I dont want to but I think so.

I feel like this drawing is out of spec on these issues and we just need to compile a list and submit to the customer for clarification. I dont know what it is, but there is always negativity when I approach management stating we need to speak with the customer for clarification. Hopefully all goes well!

Thank you guys for the help, the responses are awesome.

 

[btrueblood]

A thought: the "V" may be somebody's attempt to indicate that the specified datums are referred to in the finished (machined) condition, as opposed to an as-cast condition. It's the only use of the letter I can think of, and similarly was an old-school way of showing what features on a casting were to be machined...and led to the current form of the surface finish symbol.

 

[Occupant]

As already mentioned, I am pretty sure the "V" refers to "virtual" depending upon what the datum letters B&E refer to. And the f 3 is probably metric and indicates a finish of 125 nowadays because a 3.0 micro-inch finish for a part like this would be out of the question.

 

[3DDave]

The surface also has a separate surface finish symbol, and an identifying arrow, with a 3.2 callout. From the position, the 3.0 looks like someone forgot to move it and ran it over with another dimension extension line.

 

[gerhardl]

A machined rounded off entrance to the threading? (or am I far off? Enscribed in a circle?)

http://en.wikipedia.org/wiki/Engineering_drawing_abbreviations_and_symbols

v finish A letter v (Latin small letter v) written on a line representing a surface is a way to indicate that the surface is to be machined rather than left in the as-cast or as-forged state. The older symbol for this was a small script (italic) f (see herein f). Later the ASA convened upon a letter V (specifically a sans-serif V) touching the surface. Soon this evolved into the "check mark" sign with accompanying number that tells the reader a max roughness value (RMS, microinches or micrometres) for the machined finish, to be measured with a profilometer.

 

[tbuelna]

After taking another look at the composite positional tolerance on the attached drawing I noticed that the datum blocks are located to the left of the tolerance value. This would mean the GD&T standard used is ANSI Y14.5-1973 (or earlier). Since the 1973 GD&T standard used predates CAD systems, it is quite likely this drawing was originally done by hand and converted to CAD at some later date.

As for a "V" datum material condition modifier symbol, there is none listed in any past or current GD&T standard. In ASME Y14.5-2009 there is a "U" material condition modifier symbol indicating an unequally disposed profile.

If the document is an old legacy CAD drawing it is quite possible you have a font compatibility issue that is causing the symbol to misprint as a "V". I has seen similar problems before. If you have access to the CAD file you might try changing the font settings and see if the V symbol changes to something else.

Hope that helps.
Terry

 

[hydtools]

I don't understand the fear of negativity if what you are doing in ensuring that you will make the part the way the customer wants it rather than screw it up and have to eat the cost.

Ted

 

[3DDave]

tbuelna,

Did you also note the mismatch in datum references of the composite block between the top and bottom segments?

<Wandering off the path>
I just looked through an early work by the elder Foster. He included a rectangle with a slash as a Negative Notation alongside a datum reference as a way to indicate that the modified reference was independently used; a form of SEP REQT notation applied on a per-datum reference basis.

It's called a Treatise on Geometric & Positional Dimensioning & Tolerancing. Apparently GD&T was distinct from Positional Dimensioning and Tolerancing then. G&PD&T?

It also includes a then proposed Projected Tolerance zone symbol (P)

It really isn't much of a treatise, just a self-study guide to MIL-STD-8C and (JIMS) 1964-65 (Proposed) standards, with some additional proposed symbols. For me a treatise includes more than facts and descriptions, but also some arguments, reasoning and conclusions about those arguments.
</wandering off the path>

Back to this topic, the treatise did not have (V). My best guess is someone was working with poor quality prints and in no-brains mode, which is what most people paid to convert paper to CAD in bulk are working with, then they could easily have mistaken a blurry (M) for a (V). I've seen this in OCR software where a lower case d becomes cl.

In the case of the composite block, A and D look similar when blobbed and B and E also look similar, probably both levels should start [A|B].

 

[tbuelna]

The font issue I mentioned use to be a common problem if the CAD environment/settings used when reading the drawing file were not the same as those used to create the drawing file. Drafting symbols that are created by a certain keystroke combination (such as diameter, LMC, MMC, etc) often change when a different font is applied. I have worked at companies that performed subcontract engineering work for many different customers, and we had to use a specific CAD environment for each customer to ensure there were no compatibility issues like this.

Attached is an example of how to set up AutoCAD to produce GD&T symbols with certain keystroke combinations. As you can see it requires a specific font to be used. If the same font is not used when reading the drawing the symbol may not appear as intended. The same problem can occur when printing a CAD drawing if the printer does not recognize the font properly.

 

[resjsu]

hydtools: I agree. I cant explain the reasoning I just no what happens everytime we ask to speak with the customer tp clarify issues.

3DDave & tbuelna: These are great ideas, it never occured to me it may just be a font issue but it makes sense as we too have seen some weird font conversions over the years. If we receive a response and hopefully explanation I will post it in this thread.

Thank you all again