Meaning of T on Concentricity 2

[SeasonLee]

Please ref to the attached figure, what is the meaning of T on Concentricity callout?

Thanks for your assists

SeasonLee

 

[KENAT]

What drafting standard is it meant to be to, ASME Y14.5M-1982?

(I love the coffee stain by the way, and I'm guessing this isn't your drawing etc. but before someone else says it, it shouldn't say reamed on the .188 dia call out.)

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

 

[powerhound]

The only T modifier I know is tangent plane and it is a "circle T". If the intent was to somehow invoke "tangent plane" then this is incorrect and cannot be checked. There should be a diameter symbol before the tolerance value so that much is wrong with this specification as well.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
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[CheckerHater]

Total indicator reading / movement?

 

[powerhound]

Good point CH. Tec-ease has a tip this month about what was allowed on older standards and the word TOTAL used to be allowed in the FCF. Maybe it's a pre-1973 standard print and the T is supposed to mean "TOTAL".

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[dingy2]

T is tangent plane and is inappropriately used on concentricity.

Dave D.

http://www.qmsi.ca

 

[CheckerHater]

Judging from datum symbol the standard is 1982 or earlier, so definition was different from 94/09.

Back in time Concentricity was seen differently and where is an indicator, there is a "total".

 

[fsincox]

I agree it is most likely a left over from TIR.
Frank

 

[SeasonLee]

The only one T symbol example on the 2009 STD is FIG 6-18, which is applied on parallelism callout; can we use it on the other callout? Say flatness, straightness, or …..

SeasonLee

 

[CheckerHater]

What is the advantage of applying Tangent Plane to Internal Diameter?

 

[Belanger]

Season ... Tangent plance can't be used on flatness or straightness because the definition of tangent means that it ignores flatness/straightness. It only checks the highest points (tangent plane). The circled T can be used on parallelism, perpendicularity, angularity, and even profile of a line/surface (although the standard doesn't explicitly say profile, it's implied by the note in the text). Maybe even runout could use the T.

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

http://www.gdtseminars.com

 

[SeasonLee]

But, circle T can not applied on Concentricity callout for sure, right?

Season

 

[Belanger]

Right, because of the definition of concentricity, which specifies the "median points" of diametrically opposed elements, blah, blah...

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

http://www.gdtseminars.com

 

[SeasonLee]

One more question : When should we need the tangent plane symbol in FCF after stated tolerance.

Thanks

SeasonLee

 

[Belanger]

If you want to allow the form error to be greater than the given tolerance (such as for parallelism). An example would be a simple mating surface, where we don't really care about pits/valleys, but we do care about peaks since they will make the part sit at a different angle. Don't use T if the mating surface is a sealing surface where you are are worried about leakage.

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

http://www.gdtseminars.com

 

[SeasonLee]

Thank you all, it makes me clear in a short time.

SeasonLee