Coaxial vs concentricity 2

[BKM2]

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??

 

[KENAT]

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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[BKM2]

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.
?

 

[Belanger]

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

 

[KENAT]

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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[BKM2]

Belanger,
I'm not sure why you cant open the JPEG...I've re-saved & re-attached it. Hope it works...I look forward to your input

 

[KENAT]

Well, "Perfectly Aligned" as requested in sketch is going to be unachievable.

You don't give details of the mating piece.

I'm tempted to suggest position may be adequate.

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[BKM2]

Hey Kenat,

I've added detail to the illistration showing its mating parts/weldment. I've also attempted to give it a concentricity constraint...see attached.
Make sence??

 

[ewh]

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." - [small]Robert Hunter[/small]

 

[KENAT]

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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[ctopher]

Maybe look into Projected Tolerance Zone?

More info on runout:

http://www.tec-ease.com/tips/june-97.htm

Chris
SolidWorks 10 SP4.0
ctopher's home
SolidWorks Legion

 

[pmarc]

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)

 

[BKM2]

pmarc,

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