Circular runout on a cone with basic angle or with toleranced angle

[Crvasu]

What would be the correct callout for the circular runout on a cone, basic angle or direct toleranced angle plus-minus?

And what would be the difference between these two callouts of circular runout?
Is one controlling something and the other doesn't?

 

[3DDave]

Circular runout will not control how conical the item is if only a basic angle is used. It could be used to decrease eccentricity if a profile control is used.

 

[greenimi]

3DDave,

So, you are saying that circular runout with basic angle could be used as a refinement of the profile?
Probably something similar with figure 8-26, but applied on a cone not to a straight cylindrical surface as applied in the 2009 standard.

In other words, if angle is ± then circular runout is not a refinement and if angle is shown basic then must be some sort of “fine-tuning”?
Is my understanding correct?

 

[3DDave]

My not including an exhaustive list of other options is not the same as excluding all other cases.
I said nothing about +/- angles.

 

[Crvasu]

3DDave,
Thank you for the answer. In 2009 standard never seen circular runout used with basic angle. All I can find are with plus-minus angle.
Could you indicate an example with angle basic?
What would be the main difference?

 

[greenimi]

All,
As the OP is questioning, did you ever seen a “NEED”/application to use circular runout with basic angle? Just curious myself.

 

[powerhound]

I imagine that you wouldn't need to have a basic angle but if you are defining a cone without a basic angle then you are probably leaving some things open to interpretation since you wouldn't be locating or orienting the cone with profile of a surface. I'm sure there could be a note that describes what you mean but even that could potentially be misinterpreted.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[powerhound]

In 2009 standard never seen circular runout used with basic angle. All I can find are with plus-minus angle.

Can you cite where you saw runout used on a cone with a +/- angle? I quickly flipped through the standard and did not see one.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[greenimi]

powerhound,
Before crvasu is answering (hope he/she does not mind), I found that Fig. 9-2 / 2009 page 181 shows it.
But, again, never seen the same circular runout used with basic angle (instead of ± angle)

 

[powerhound]

Oh, I see it now. I can also see how this is actually not as bad as I thought it could potentially be. Thanks.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[pylfrm]

For a circular runout tolerance applied to a conical surface, the ASME Y14.5.1M-1994 tolerance definition involves the nominal angle of the contour. Presumably the following dimensioning methods would all be sufficient to establish a nominal angle of 12.3°:
[ul]
[li]12.3° +/- 0.4°[/li]
[li]12.3° +0.4° / -0.5°[/li]
[li]12.3° +0.4° / -0°[/li]
[li]12.3° +0° / -0.5°[/li]
[li]12.3° +0.5° / +0.4°[/li]
[li]12.3° -0.4° / -0.5°[/li]
[li]12.3° BASIC[/li]
[/ul]

But the following method would probably not be sufficient to establish a nominal angle:
[ul]
[li]11.9° - 12.7°[/li]
[/ul]

As long is the nominal angle is provided somehow, there should be no difference in the meaning of the circular runout tolerance.

For minimum ambiguity, I'd recommend using a basic angle. If a toleranced angle is desired, I'd recommend expressing it using the first method shown above.


pylfrm

 

[3DDave]

Circular runout and a basic angle do not control the allowable envelope of the conical feature. I don't see where a nominal angle has any special meaning. It's too bad there is no definition for "true geometric shape" as mentioned in Figure 9-2.

 

[pylfrm]

3DDave,

I only looked at ASME Y14.5.1M-1994 because I didn't find a useful definition of the tolerance zone orientation in ASME Y14.5-2009. Using an undefined term like "true geometric shape" is the opposite of useful.

Unfortunately ASME Y14.5.1M-1994 does seem to give special meaning to nominal dimensions in this context:

Nominal diameters, and (as applicable) lengths, radii, and angles establish a cross-sectional desired contour having perfect form and orientation. The desired contour may be translated axially and/or radially, but may not be tilted or scaled with respect to the datum axis.

The tolerance zone for each circular element on a surface constructed around a datum axis is generated by revolving a line segment about the datum axis. The line segment is normal to the desired surface and is of length t₀, where t₀ is the specified tolerance.

I can only assume the "desired surface" is generated by revolving the "desired contour" about the datum axis.

The whole section seems like a bit of a mess to me.


pylfrm

 

[3DDave]

Might as well be in a basement with the stairs torn out, the light bulbs removed, in a locked room, at the bottom of a sealed file cabinet in a mislabeled folder. Guarded by a leopard.

While it might have been a kindness for casual users to remove all the dot and cross product descriptions to its own document, it did the users a disservice by adding their own unsupported explanations that were not coordinated with the Y14.5 document.

 

[CheckerHater]

Agree with 3DDave: combination "basic angle/runout" makes no sense.

@pylfrm: according to ASME Y14.5-2009 Para. 1.3.56 Size, Nominal "size, nominal: the designation used for purposes of general identification"

It's not even dimension. It's like "2 X 4" and we both know how 2 X 4 actually measures. So don't place lot of hope into "nominal" dimensions.

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

 

[pmarc]

Regarding fig. 9-2, it is a shame that the standard shows +/- angular dimension applied this way in the first place.

 

[Crvasu]

Pmarc,
Since I am new here, please forgive me for asking: how would you use circular runout? With basic dimension?
If yes, how to combine it with size dimension?

 

[pylfrm]

3DDave,

I generally agree about the leopard. I think the effort put into Y14.5.1 could have been more profitably spent on better English definitions for Y14.5.


CheckerHater,

Consider ASME Y14.5-2009 Fig. 8-18, and imagine the diameter 24 +/- 0.2 dimension is changed to basic. I think it would be perfectly valid to add a circular runout tolerance applied to the conical surface and referencing datum feature A. Do you see a problem with that?


pylfrm

 

[greenimi]

Pmarc,
Welcome back!
I checked ISO 1101-2017 and circular runout is not shown neither with +/- angular dimension or basic angle. Why is that? Maybe because ISO treats cones as feature of size?

However, when circular runout is used in a specified direction half-angle is basic.

Hmm, just trying to understand the concept.

Pylfrm,

In your modified ( basic 24 instead of plus/minus) fig 8-18 case would you use circular runout as refinament of the existing profile?

What about if removing profile entirelly? Will it became underdefined then?

 

[pylfrm]

greenimi,

Circular runout would be a separate tolerance. I wouldn't call it refinement. I think that term is unhelpful at best in most GD&T contexts. Does that answer your question, or are you getting at something other than terminology?

The circular runout tolerance will not become under-defined if the profile tolerance is removed. Its meaning will not change. If no other tolerances are applied to the cone, then the requirements of that surface would probably be under-defined.


pylfrm