# Thread: What is the correct way to tolerance this True Position callout on a bolt hole circle

1. ## What is the correct way to tolerance this True Position callout on a bolt hole circle

I believe the intent of this callout is as follows:

The 44.050 to 44.030 means this is a stud not a hole. ( old school drawing )

The 0.04 true position is for the stud that it is pointing which is also now a tertiary datum.

The 0.07 true position is the other 7 studs

The 0.02 true position is for the studs to themselves aligned through the first hole.

2. With only the three feature control frames shown - I take your word on the interpretation.

We would need to see all of the associated details to give an provide comment.

3. Originally Posted by Kelly Bramble
With only the three feature control frames shown - I take your word on the interpretation.

We would need to see all of the associated details to give an provide comment.
I am trying to get the whole view now.

4. Do you know what that round symbol means on the right side of the control frame? It almost looks like concentricity but there seems to be a break in the line at the 4 o'clock position????

5. It's an "at" symbol

@ = at

6. I thought so too and felt silly asking what the @ sign is for. So what its meaning on a drawing?

Thanks Kelly for the help,its truly appreciated.

The only thing I can think of it that its print specific and has its own meaning like the diamonds to the left side.

7. Originally Posted by Paul Sarrach
So what its meaning on a drawing?
The indicated geometric tolerance applies "at" some specified location, locations or feature who knows...

Maybe it only applies on Tuesdays "at" 3:00 am...

Again, you have posted an incomplete drawing..

8. Where can I read something that states that? I understand its incomplete I am helping a friend on the other side of the world so our timelines are not in sync.

Even if its incomplete have you ever seen a 3 compound true position callout that shows two T/P's to the same alignment with two different sizes and the third to itself? If you have what did what was you interpretation? If not what book do I need to get?

9. Originally Posted by Paul Sarrach
If not what book do I need to get?

All of the books I have authored have examples utilizing "@". The books identified with ** will have examples that include multiple feature Control Frames.

• Geometric Boundaries SI, Interpretation and Application, per.ASME Y14.5M-1994 **
• Geometric Boundaries, Interpretation and Application per.ASME Y14.5M-1994 **
• Geometric Metrology - Dimensional Tolerances Inspection
• Geometric Boundaries II, Interpretation and Application per. ASME Y14.5-2009 **
• Engineering Design and Manufacturing and Assembly, DFM/DFMA 2007-2015

Other industry standards:

• ASME Y14.5-2009 Dimensioning and Tolerancing Standard **
• ISO 1101-2009, Geometrical Tolerancing **

BTW, I am ASME certified at the senior level GDTP since 1997 I think.

See:

http://files.asme.org/asmeorg/Codes/...onnel/8951.pdf

Also, I have delivered GD&T as well as DFM/DFMA training classes all over the world..

See:

http://www.engineersedge.com/GDT_Training.htm

http://www.engineersedge.com/trainin...g-training.htm

10. That's way awesome, its my privilege and honor to chat and have your support and guidance.

Where might I find this book? Geometric Metrology - Dimensional Tolerances Inspection for sale?

They are going to order this: ISO 1101-2009, Geometrical Tolerancing because the cannot find their copy ergo why I am here. But I am not so sure that that book will answer this question. Have a good night Kelly.

11. I'm just joining in here, so let me go back to the beginning...

There is nothing on that snapshot to indicate whether they are studs or holes. (You mention some "old-school" rule, but I don't get that; the rule is simply that the larger number always goes above the smaller number, regardless of hole vs. pin.)

Then, the triple callout right now seems bogus because you can't have two different tolerance numbers for position referencing the exact same datums in the exact same order D, E, F. In the ASME system this is often done but you'd show one position symbol vertically centered between the two frames.

The key is the "at" symbol -- as Kelly wrote, perhaps it qualifies each line with a special condition that would make them different requirements. So it might be legal if we see the wider picture.

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