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Coaxial vs concentricity
2

Coaxial vs concentricity

Coaxial vs concentricity

(OP)
I work for a company that is just starting to use GD&T and am have & issue on how to detail 2 coaxial "hinge points".
In the past we have had problems with these 2 points actually being "coaxial" during assembly. Can anyone please advise me as to how best detail the hinge points in the attached drawing. Coaxial or concentricity??
 

RE: Coaxial vs concentricity

Your image wouldn't open.

'Coaxial' is a generic term for when 2 or more cylindrical (or similar such as cone) features share a common axis.

Coaxiality can be controlled by a number of geometric controls such as position, run out, total run out and concentricity.

Concentricity is a specific Geometric Control with fairly limited application as it relates to the theoretical axis rather than the 'real' surface of the cylindrical features.

While it needs to decided based upon function, position controls are often adequate and are usually my first choice unless there is a strong functional requirement in which case I'd consider run-out as my next choice.

It really needs to be decided based on function which I con't know.

What standards are you using, ASME or ISO?

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RE: Coaxial vs concentricity

(OP)
Tks Kenat for your input,

I've saved the illistration in a different format (JPEG) and re-attached it for your consideration.

I understand & appreciate what your saying, but am still unsure how to correctly detail the attached...Im leaninging toward concentricity.
?

RE: Coaxial vs concentricity

Still can't see the graphic -- make sure it has  .jpg  at the end of the file name?

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

RE: Coaxial vs concentricity

I still can't get it to open, may be a fault at my end though normally I open stuff on engineering.com OK.

Take a look at whatever standard you're using as this might be a place that ASME & ISO differ but I can't recall for sure.

Concentricity would normally be my last choice, I'm not expert enough to fully explain that but per ASME & according to some fairly smart folks I've known, it has very limited real world application.

I'd really look at position or runout.

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RE: Coaxial vs concentricity

You should probably investigate just what will be required to inspect concentricity vs position before you make it a requirement.

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

RE: Coaxial vs concentricity

Take a look at section of 5.11 7 5.12 of ASME Y14.5M-1994 if that's the standard you are using.  It discourages use of concentricity in favor of position or runout.

I'd lean toward position control for your application but it's not a situation I've really dealt with.

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RE: Coaxial vs concentricity

As I posted today in thread entitled "True position callout" there are at least two additional methods of assigning two or more features coaxial:
1. By using CF (continuous feature) symbol, which is quite new concept, but makes two or more features of size as a single one. (See fig. 2-9 in Y14.5-2009)
2. By applying 0 position tolerance at MMC without any datum reference to .402-.406 dim., which will also work in similar way. (See fig. 4-24 in Y14.5-2009)

RE: Coaxial vs concentricity

(OP)
pmarc,

I appreciate your input; however, I don't have acess to Y14.5

 

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