application of total run-out

[Bill B.]

Total run-out interpretation.
I’ve been lurking on this forum for several months and I am impressed with the wealth of knowledge the members bring to the forum. My understanding of the standard has grown as a result. The standard I am referencing in the example is the ASME-Y14.5-2009. For background let me state that the part design is controlled by our customer, with one exception, that is the size of the spherical radius which is under our design control. As such the customer could not use profile to control the spherical radius and instead chose to use total run-out.
My understanding is that run-out, both circular and total, only control radial elements of the feature and not axial. However 9.4.2.1 states that total run-out may be used to control profile of a surface, which has me questioning whether my understanding is correct.
Looking at the example I have several questions:
1. What would a datum simulator for B,A look like? Is this a valid call out or should it be either A,B or just B ( there are no other FCF’s that use B,A so the intent would not be to create a simultaneous requirement)
2. Is this a legitimate use total run-out
3. If #2 is yes, Does total run-out control the 1.00 basic from datum A

I would like to thank everybody in advance for your comments and help.

 

[Jacob Cheverie]

Bill,

Runout requires a datum axis, whereas you have two planar datums. That being said, I would say no to #2. It looks to me like you would want a Position.

 

[Bill B.]

Jacob, Datum feature B is a diameter

 

[chez311]

Bill,

Specification of datum features should replicate function. If |B|A| best represents part assembly/function then go ahead an utilize that - your simulators of |B|A| vs |A|B| would look like the difference between Y14.5-2009 fig 4-21(b) and fig 4-20(b). That said, if the only reason you are utilizing |B|A| is because you don't want to create a Simultaneous Requirement with another FCF utilizing |A|B| or |B| then the standard gives us a mechanism for that - namely the SEP REQT notation to indicate Separate Requirements.

My understanding is that run-out, both circular and total, only control radial elements of the feature and not axial.

Runout, both circular and total, may be utilized to control axial elements on a surface perpendicular to the datum axis. See the .04 total runout on fig 9-5. Circular runout can certainly be utilized to control elements of a complex shape such as the .08 circular runout specification on the same figure, but it is not so clear cut for total runout.

Some will give you pushback, but there is nothing in the Y14.5 standard which specifically states it cannot be applied to a complex shape such as a spherical radius - the only evidence being that there are no examples of it in the standard. Additionally, the equations and definitions provided in the math standard Y14.5.1 for total runout can be applied to any revolute shape created around an axis. That said, if you utilize the 2018 version a new modifier has been added to profile called the dynamic profile tolerance modifier. This is essentially generalized runout and can be applied to any shape and does not have the limitations of runout (does not require a datum axis).

 

[Belanger]

I would hesitate to use total runout in this context. It's not because the standard never shows any such examples -- my issue is how to get the dial indicator to follow the curvature of that spherical shape. A spherical shape is more than just form and location; it now gets into size variation (the SR).

In the past we've discussed here whether it's possible to use total runout on a cone. This might be an offshoot of that idea, but with a more complicated shape.

Chez311 brings up the best option, though. If you could somehow throw the switch to the 2018 standard, your sketch would be a great candidate for "dynamic profile."

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[Bill B.]

chez311,

Thank you sir. The examples sited where very helpful. The only thing I'm not clear on is the distance from the face (1.00 basic) controlled using total runout? Figure 4-21(b)would indicate that it is.

 

[pmarc]

Bill B.,

Runout tolerances never control axial location of the toleranced features.

In your example, the spherical feature can be at any distance from datum plane A and still meet the runout tolerance. In other words, the basic 1.00 dimension is meaningless for the runout tolerance.

 

[greenimi]

pmarc,

I am not sure, but maybe Bill B is confused about fig 8-26/2009 where circular runout 0.15 is applied on a surface with basic dimension Ø20, but I will say that in the picture's standard Ø20 basic is for the profile 0.25 and not for the runout 0.15 (which runout is just refinement of the profile).

 

[pmarc]

greenimi,
I am not sure if this is what Bill is confused about, but in fig. 8-26 the axial location of the contour is controlled by the profile tolerance.

 

[Bill B.]

Thank you for the comments, my understanding based on the comments is: the runout would control the form of the spherical radius and would control the location in relation to the datum axis but not the distance from the face (datum feature A).

I have additional questions:
1. If the distance from the face is not considered, what does using datum A as a secondary datum in the FCF do? How would you stage the part differently if only datum B used?
2. How would you inspect this? We run Nikon CMM's and I am being told by our programmers that Camio will not support this type of measurement

 

[chez311]

JP,
I agree - total runout measured with a dial indicator in this case would require a pretty elaborate setup. Use of a CMM would almost certainly be a prerequisite, assuming the software can handle it (per Bill's latest comment). Another reason to avoid it might be simply because one might have a tough time convincing others it is legitimate.

Bill B.,
For the reasons above, it may be worthwhile to reconsider your use of total runout. Either circular runout combined with profile or even a multiple single segment/composite profile might be more viable and easier to swallow alternatives if you cannot go by the 2018 standard and can accept the limitations/differences of these controls compared to total runout.

 

[pmarc]

Bill B.
Datum A secondary in the current callout adds no value.

 

[chez311]

pmarc,

For whatever reason I'm questioning whether it is as clear cut as that, though I had always thought the same (runout does not provide z location constraint along the axis, only x/y perpendicular to the axis). If we assume that total runout is essentially a subset of dynamic profile (or dynamic profile as a generalization of total runout) then it would be constrained in axial location unless a customized DRF were utilized. That said, I have seen in at least one special case there can be some subtle differences between these two though - this would be a major difference. Additionally to support this difference even the equations in Y14.5.1-1994 only references a tolerance zone revolved around a datum axis - no considerations for location constraint to a datum constructed at a right angle to the datum axis (or the inverse), suggesting that the addition of a primary planar datum feature serves only to orient said datum axis/tolerance zone and not constrain it in location. This would explain also why the only planar datum features referenced in the runout section of Y14.5 are primary.

I was initially hoping it would provide some clarity but I'm somewhat flummoxed by the verbiage in Y14.5.1 for the definition of runout (which its worth noting has been unchanged in the draft). What is the distinction between axial/radial translation and scaling here? Seems to me the tolerance zone should be at the very least constrained in radial translation and allowed to scale wrt the datum axis, but the verbiage seems to suggest otherwise, unless these terms are being used in a different way than I expect.

Evaluation of runout (especially total runout) on tapered or contoured surfaces requires establishment of actual mating normals. 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.

 

[axym]

Bill B.,

I don't think that you will be able to get a reliable answer for questions 2 or 3. The runout section of Y14.5 just doesn't say enough about situations like this, and extending what they do say always involves some degree of guesswork and assumptions. It's a can of worms. This is a geometric tolerance that evolved from shop-floor dial indicator checks on a lathe, for cylindrical and planar features. There is not even consensus on whether or not total runout can be applied to cones.

I agree that the dynamic profile tool in Y14.5-2018 would address the sphere application without ambiguity. It would control the sphere's form, radial location to B, and axial location to A - everything except its size.

Now that the more rigorous dynamic profile tool exists, I think that the definitions in the runout section will remain as they are.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[3DDave]

As much fun as the dynamic profile must be to use, what industry has been crippled these last 70 years that they have had to make-do without it? Are there cases where people say - I don't care what the size is as long as it scaled nicely?

 

[pmarc]

If we assume that total runout is essentially a subset of dynamic profile (or dynamic profile as a generalization of total runout) then it would be constrained in axial location unless a customized DRF were utilized.

So perhaps it is a good reason not to assume that dynamic profile is a generalization of total runout.

If we assume that a flat surface nominally perpendicular to the datum axis is a special case of a surface of revolution (i.e. a cone with 180 degrees included angle), then according to what you seem to be saying a total runout tolerance applied to it should also control location of the surface relative to the referenced planar datum, am I right?

So in that case, why in your opinion para. 12.4.2(b) in 2018, which says that: "(b) When applied to surfaces constructed at right angles to the datum axis, total runout controls cumulative variations such as flatness, straightness, and perpendicularity (to detect wobble) of a planar surface.", does not mention anything about total runout also controlling location of the surface?

 

[greenimi]

pmarc,

I know for sure that we talked about the "location of the surface" or "Location of Entire Surface" as shown in the table / figure 12-6/ 2018.
I not don't know EXACTLY, but I think has been decided that the wording is just less than perfect.

greenimi,

I agree that statements such as "location of entire surface" muddy the waters. So we need to look past those statements and find the more geometric/mathematical descriptions of the tolerance zone. The new draft also states the following:

"All surface elements shall be within a tolerance zone consisting of two coaxial cylinders with a radial separation equal to the tolerance value specified. The tolerance zone is constrained in translation (coaxial) to the datum axis."

This definition nails it down - it describes well-defined pieces of geometry that behave in a certain way. So we can end the controversy over what "location of entire surface" means. It must mean whatever makes it agree with the geometric/mathematical definition.
Evan Janeshewski

https://www.eng-tips.com/viewthread.cfm?qid=430633

 

[pmarc]

greenimi,

The words used in rows 1 and 2 in the table under figure 12-6 are indeed less than perfect, but the undeniable fact is that all 4 runout tolerances shown in that figure define tolerance zones which are centered at the datum axis. And to me this goes along well with para. 12.4.2(a) which says: "a) When applied to surfaces constructed around a datum axis, total runout controls cumulative variations such as circularity, cylindricity, straightness, and location (coaxiality) of a cylindrical surface."

For planar surfaces, however, para. 12.4.2(b), quoted by me previously, mentions nothing about any type of location control (in particular axial location). So if total runout does not control axial location in case of planar surfaces, then I don't see how it could control axial location in case of surfaces of revolution.

 

[axym]

All,

Runout tolerances are built on the concept of FIM (Full Indicator Movement). In terms of tolerance zones, the equivalent of FIM is that the tolerance zone is allowed to offset (Y14.5 uses the term "progress".

One difficulty with runout tolerancing is that most of the feature types that runout deals with are special cases in some way.

The cylinder is a special case because offsetting the cylindrical-shell zone looks the same as expanding/contracting it radially. The zone is also parallel to the datum axis, so a planar datum feature can have no effect.

The cone is a special case because offsetting the conical-shell zone looks the same as expanding it radially or translating it axially (if we are willing to increase the zone's extent). So the total runout zone cannot control the location of the cone relative to the planar datum (if total runout had been specified). This is an issue in the "conicity" figures in the profile section as well.

The planar surface is a special case because offsetting the planar-shell zone looks the same as translating it axially. So a total runout zone would not control the location of the planar surface relative to the planar datum.

We need to see what happens in a more general case (such as the curved surface in Fig. 12-10) to really know what the effect of a planar datum feature is. If total runout was specified on this feature, would the zone be allowed to translate relative to datum D? We don't know, because there is no example in Y14.5 with a feature like this (intentionally, I believe).

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[chez311]

So perhaps it is a good reason not to assume that dynamic profile is a generalization of total runout.

I'm not going to disagree with you necessarily - I'm just constantly comparing the two when I think about special cases like this. As I said I already know there can be some differences, and perhaps this is one of them. With a runout control it could make sense that we only care about location of the tolerance zone wrt a datum axis and not axially along its length. That said, as Evan pointed out, I don't think the standard is clear on this point - we can only infer.

If we assume that a flat surface nominally perpendicular to the datum axis is a special case of a surface of revolution (i.e. a cone with 180 degrees included angle), then according to what you seem to be saying a total runout tolerance applied to it should also control location of the surface relative to the referenced planar datum, am I right?

Evan got to it before me, but his response aligns pretty much with what I think in this regard after several lengthy discussions on the topic such as (

https://www.eng-tips.com/viewthread.cfm?qid=448819)

and (

https://www.eng-tips.com/viewthread.cfm?qid=460248).

A tolerance zone could be uniformly offset from a planar true profile such that this uniform offset is indistinguishable from translation, the same as it would be for a conical/tapered feature (as you noted - I agree a planar feature could be considered a cone with 180 degrees included angle).

I apologize for opening the can of worms, but I had taken it for granted that axial location with runout was not controlled. After considering it again due to OP's inquiry I found myself questioning it again in light of the above and was hoping to find a more definitive answer in the standard and did not find it. Turning to the math standard I found myself even more confused by some of the verbiage. I do see the merits for the argument saying a runout tolerance zone should not be constrained in location axially though.