Unkown symbol on drawing

[robertadc]

I have a drawing that has a circle with a horizontal line across it when specifying a range of dimensions (see attached picture). This is done for a diameter as well as linear dimensions. Does anyone know what this means? It is from a GE drawing.

I'm sure if I stay within the limits, it will not matter. But I wonder if it is acceptable to go over by a small amount, such as 0.5531 in the example?

Robert

 

[PeterStock]

I am thinking, but not having worked at GE I do not know, it indicates that the dimension is critical to function, safety or customer in some way. It is likely that it is to some sort of GE spec. Ask for a clarification.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[pmarc]

The symbol looks like incomplete datum target symbol.

According to ASME Y14.5 all numerical values are absolute, so if 0.553 is specified on the drawing, it means 0.5530....00. If the measurement is 0.5531, then the part is out-of-spec.

 

[KENAT]

Quick look through Genium Manual which is based on the GE didn't appear to have anything like that except for Datum Targets though I didn't look too deeply.

Assuming it conforms generaly to ASME Y14.5m-94 or similar (does it say on the print?) then .5531 would not be acceptable, the upper limit is .55300000000000000000000000000000000000000000000000000000... regardless of that symbol.

Posting guidelines faq731-376

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

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

 

[Belanger]

Perhaps just a goofed-up diameter symbol. Was the drawing translated from another CAD program?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[MechNorth]

I'm of a like mind with JP on this one. I vaguely recall early versions of some CAD packages (V2 Autocad & an early CadKey?) used a symbol like that for diameter.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[KENAT]

I thought that, but then why tag DIA on the end?

Posting guidelines faq731-376

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

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

 

[fcsuper]

It's not likely for diameter since the OP stated "This is done for a diameter as well as linear dimensions."

When uncommon symbols are used, they should be defined in the drawing's notes. This is true even if they are a "company standard", since others are not likely to know what it means outside of the context of that company. At my company, we use an eyeball to ID inspection points. On each drawing where an eyeball appears, there is a general note that explains what it means. (yes, it is creepy when I put two eyeball symbols next to each other...thankfully there's no reason to ever do that on a real drawing.)

I guess a company could refer to their own standard within the drawing, but that would still have to be stated on the drawing, and copies of that standard would have to be made available to vendors and customers alike.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[MechNorth]

Missed that, Matt. Tks. Mind posting your eye-ball?

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[fcsuper]

Eyeball symbol is available here:

http://sw.fcsuper.com/index.php?name=UpDownload&req=viewdownloaddetails&lid=84

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[fcsuper]

Sorry, I just realized I was posting this comment in the general Drafting Standards forum. That eyeball file is for SolidWorks.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

http://groups.yahoo.com/group/solidworks & http://twitter.com/fcsuper

 

[looslib]

How old is the drawing from GE?
I am working at GE/Energy on NX and using some Inventor and I haven't seen that symbol in the year I have been here.



"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[robertadc]

"Assuming it conforms generaly to ASME Y14.5m-94 or similar (does it say on the print?) then .5531 would not be acceptable, the upper limit is .55300000000000000000000000000000000000000000000000000000... regardless of that symbol."

Yes, ANSI Y14.5M applies (it doesn't say which version, I assume the newest).

It is fine to say that .553 is an absolute limit for interpreting the drawing, but is it really the limit for a finished part? If so, I guess I am actually restricted to some amount less depending on the accuracy of my measuring equipment.

For example, if a linear dimension is 0.552-0.553 and I try to measure this with calipers with an accuracy of +/-.001, there is no way I can be sure the part is good. If I measure with micrometers with an accuracy of +/-.0001, then I can only say the part is good if it reads between .5521 and .5529. Is this right?

Robert

 

[robertadc]

The drawing is from 1986. It looks like it is hand drawn except for some pre-printed blocks and general notes.

 

[pmarc]

If ANSI Y14.5M applies and the drawing is from 1986, than it should be according to 1982 version.

Your statement that you are "restricted to some amount less depending on the accuracy of my measuring equipment" is correct. But you are not quite correct by saying that there is no way to be sure the part is good when measured with caliper with an accuracy of +/-0.001. You can always have reading 0.552 or 0.553 and then the part would be OK.

If you measure with micrometer with accuracy of +/-0.0001, then the reading can be somewhere between 0.5520 and 0.5530, not 0.5521-0.5529.

 

[ewh]

I agree that it is not wise to assume that it is to the lastest version. We currently design to the '94 version even though it isn't the latest.
This points out how important it is to include the date of the standard when specifying what standard to use for interpretation.

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

 

[MechNorth]

Tks Matt. I can see why it'd be a bit creepy with a pair on a drawing ... maybe add a maniacal monocle to one of them? I think I'll do something similar to use as a stamp in Adobe when I want a client to pay attention to something.

You can't assume it's '82 compliant just because it's made after '82; there's still folks out there working to the '60s version. If it has the "M" modifier on Y14.5, then by deduction it would be the '94 version; that's the only one that has the "M" modifier. Though I'm not sure that would stand up in court.

As for whether or not you can live with 0.0001, which likely would be eaten up by your measurement system accuracy ... it's up to the user's risk aversion. If the part could fail because it is 0.0001 or thereabouts out of spec, you likely will be risk averse and not accept it. On the otherhand, if it's a clearance hole and you can live with more, then it's a fairly safe move to accept it.

Now, as for the issue of how to measure it, per Rule #1; full form check at MMC and two-point check at LMC (Taylor's Principle). Don't know if it's a hole or a pin, but a caliper measurement would only be valid (i.e. in compliance with Y14.5 ... any version that I'm aware of) for the LMC size.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[robertadc]

MechNorth,

I don't understand what you mean when you say that calipers would only be acceptable for measuring LMC. Do you mean that they could only be used to verify that the part is not too small? I should also point out that for measuring the width, the part is small enough that the entire part fits between the jaws of the clipers so they would be reading the highs of the part.

 

[robertadc]

That should be calipers not clipers. Is there no edit feature?

 

[dgallup]

Generally speaking, your measurement system must be able to resolve to 1/10 or better of your tolerance.