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# Concentricity Callout. What does it mean?

## Concentricity Callout. What does it mean?

(OP)
Hi All,
I see this callout on a part I'm checking. I've not seen the way it called out for concentricity like this. Does it mean center of 3 .250"Holes (Boldcircle) concentric to |B|?
(Normally, I see concentricity of 2 circles at the same locations.)
Thanks!

### RE: Concentricity Callout. What does it mean?

I would ask if you work to ISO or ASME (because definition of concentricity is different in two), but you are right either way: the call-out you are showing is wrong in both of them.

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

### RE: Concentricity Callout. What does it mean?

(OP)
We are working to ASME.
If it means the boldcircle (of 3x .250" holes) concentric to |B| then I just added a yellow boldcircle to the sketch.
But I still don't understand why concentricity while True Position is already called out? It may tight up the tolerances and could add composite tolerance for those 3 holes....
Any idea to this callout?

### RE: Concentricity Callout. What does it mean?

cmmguy75,

Are the holes centre-bored? I am trying to make sense of datum C. It is logical that a centre-bore should be concentric with the through hole, although a location tolerance would work just as well.

--
JHG

### RE: Concentricity Callout. What does it mean?

I guess OP's major concern is holes being "concentric" with [B]

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

### RE: Concentricity Callout. What does it mean?

(OP)
Drawoh: Datum C is a Cbore.
CheckerHater: Yes, you're correct. The concern is the 3 holes, .250" to |B|.

### RE: Concentricity Callout. What does it mean?

cmmguy75,

Your pitch circle is imaginary. You cannot apply a tolerance to it, particularly concentricity. You can apply positional tolerances to the individual holes.

--
JHG

### RE: Concentricity Callout. What does it mean?

Just echoing everyone else...this is a bad callout. There's no reconciling it either drawing. The way to correctly tolerance the hole pattern is pretty straight forward. Do you have a copy of the ASME GD&T standard?

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

### RE: Concentricity Callout. What does it mean?

(OP)
powerhound: Yes, I do have that standard.
I will find out what the mating part will do to this part.

### RE: Concentricity Callout. What does it mean?

page 137 in the 94 standard, page 121 in the 2009.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

### RE: Concentricity Callout. What does it mean?

(OP)
Thanks John (powerhound).
To my understanding, the design would go with fig 7-26 (on p122 in the 2009).
The main thing is they want each .250"hole concentric to the cbore, |C|.
Anyway, the callout is NOT right.
Thanks for all of your guys' help.
Have a great day!

### RE: Concentricity Callout. What does it mean?

I don't think the really want concentricity as the holes would all be in the same location, effectively being one hole in the center of the part.
You are right that fig. 7-26 is most likely what they need.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

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