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Difference between axial total runout and perpendicularity

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semiond

semiond

Mechanical
Jan 9, 2011
176
Hi all,
A part is consisted of two coaxial cylindrical features. Is there any difference between the following callouts:

1. Perpendicularity on the end face of one of the features to a datum axis of the other feature.
2. Total axial runout on the same end face to the datum axis.

In terms of the tolerance zone shape, it looks like they are the same, but i might be missing something?
 
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They are the same

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
 
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The only difference is the measurement method. Runout is the only GDT spec that mandates a specific method of measurement.
 
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Such as?

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

The runout tolerances are defined in terms of Full Indicator Movement (FIM), but this does not mandate that an indicator be used. In Y14.5-2009 Section 9.2, there is a note stating the following:

"NOTE: the figures in this Section use measurement techniques to explain the tolerance zones. It is neither the intent nor within the scope of this Standard to define measurement methods."

In the new Y14.5 draft, the indicator descriptions have been replaced by direct descriptions and illustrations of the tolerance zones.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
 
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I'm with CH - the standard actually clearly states it is not within the scope to define measurement methods. Its right there in the beginning of the runout section, see below.

runout_is40ht.jpg
 
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looks like i posted the same answer as Evan, I was just a bit slower to the draw - my apologies!

as an aside, could the one advantage/difference in specifying runout vs. perpendicularity on an axial feature is that it could allow you to only control a portion of the surface as is shown in Figure 9-2 (ie: could just control the portion of the axial feature furthest from the axis of rotation instead of the entire surface)? I don't see anything in the orientation/perpendicularity section allowing this, but admittedly that was from a relatively brief search.
 
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One can use a chain line to indicate a limited area for application of a tolerance.
 
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Evan,
Speaking about circularity and the new y14.5 draft, (and the form errors being one of my not so clear GD&T definitions) is it true that the definition is going to be changed to mandate UAME axis?
I do not have the draft in front of me and I am going by the memory,but I remember in one of the figures in the "Means this" sections UAME is mentioned. I compared the equivalent figure in 2009 and the UAME is missing (again missing in 2009). Is this addition of UAME in the new draft done intentionally or is one of the zillion mistakes they made up to that point?
 
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Pmarc,
I copied "zillion mistakes they made up to that point" from one of your previous posts (not related with circularity, but related with the new draft).
Sorry, but your phrase fit the best here too or I am being too lazy to think of something else. Too tired today.
 
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Is the reason for the new Y14.5 because ISO released one and the Y14.5 committee feels it needs to keep up? Has there been a sudden need to repair some previously unidentified flaw that escaped notice in the last half a century? Or is it time to get a new round of training materials published by the consultants? Yes - I'm that jaded and cynical. Just call it done and fold the standard and let ISO do the work.
 
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CH,

The ANSI B89.3.1 standard is actually referenced in a note in the circularity section (5.4.3) of Y14.5.

greenimi,

I don't believe that the circularity definition is going to be changed to mandate that the UAME axis be used. The cross sections are still defined as normal to an axis or spine (curved line), but for some reason this statement was moved out of the circularity section and into the definitions section. I believe that you're correct that one of the new figures mentions the axis of the unrelated actual mating envelope (even for a cone) and doesn't mention a spine. This is an unfortunate oversight. Technically the definitions are represented by the text, and the figures are for illustration only. So I believe that the end result is that the definition is the same as it was before, but it might be more confusing.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
 
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Further questions regarding runout and perpendicularity, if both Fig.9-4 and 9-5 runout callout means perpendicularity, what is the differences between them?

Circular_and_Total_Runout_lzfnoe.jpg


Season
 
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Total runout on an axial face is the same thing as perpendicularity. Circular runout is not.

The noted callout (on the axial face) in 9-4 is circular runout which controls each circular element on the noted perpendicular face, however it does not control the surface as a whole and therefore it IS NOT the same as perpendicularity as the tolerance zone is different. I don't think there is another symbol that accomplishes the same thing as circular runout on an axial face.

The noted callout (on the axial face) in 9-5 is total runout which controls all surface elements together and therefore IS the same as perpendicularity as the tolerance zone is identical.
 
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Thanks for your comments, chez311, if the Total Runout on the axial face in Fig.9-5 replaced with Circular Runout callout, will it control the perpendicularity or not?

Season
 
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No, you need total runout.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
 
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Thanks, dgallup, I know Total Runout will control the perpendicularity in Fig.9-5, but what is the meaning if replaced with a Circular Runout callout, will it also control perpendicularity here?

Season
 
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SeasonLee,
If total runout on the end face at fig. 9-5 was replaced with circular runout, it would control variation in axial direction along separate circular elements of the surface.
That face could be produced having conical geometry instead of flat, and still have very good circular runout.
 
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