Surface location
Surface location
(OP)
Relatively new working with GD&T and on this forum.
ASME Y14.5-2009
Does the total runout (as a lonely requirement) shown control the surface location?
Again, the surface LOCATION, not the axis location (coaxiality).
Or the surface location is controlled by the combination between the total runout and size? (not the total runout by itself as a stand-alone callout/ requirement) ?
As we know, runout does not separate form and location deviations, so the amount each of these deviations contribute to the runout deviation will not be known. The verification of a runout tolerance reports the cumulative effects of form and axis offset. But the question is about the surface location.
Y14.5-2009 states:
9.4.2.1 Applied to Surfaces Around an Axis. Where
applied to surfaces, constructed around a datum axis,
total runout may be used to control cumulative variations
such as circularity, straightness, coaxiality, angularity,
taper, and profile of a surface.
ASME Y14.5-2009
Does the total runout (as a lonely requirement) shown control the surface location?
Again, the surface LOCATION, not the axis location (coaxiality).
Or the surface location is controlled by the combination between the total runout and size? (not the total runout by itself as a stand-alone callout/ requirement) ?
As we know, runout does not separate form and location deviations, so the amount each of these deviations contribute to the runout deviation will not be known. The verification of a runout tolerance reports the cumulative effects of form and axis offset. But the question is about the surface location.
Y14.5-2009 states:
9.4.2.1 Applied to Surfaces Around an Axis. Where
applied to surfaces, constructed around a datum axis,
total runout may be used to control cumulative variations
such as circularity, straightness, coaxiality, angularity,
taper, and profile of a surface.





RE: Surface location
So the total runout in your attachment controls the radial location of the surface but doesn't control where it is axially located.
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
RE: Surface location
My follow up question is: (see revised sketch, attachment)
Can we, NOW, consider that the surface is fully located by the total runout ONLY?
As I stated before, can the total runout, as shown in the attachment, control the SURFACE LOCATION as an independent control? Or the surface location is controlled by the combination between the total runout and size?
RE: Surface location
Thus in your drawing, runout controls coaxiality and also the form of the feature. It controls the radial location of the specified surface, not the axial location.
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
RE: Surface location
RE: Surface location
I would be cautious with general statements like this. The design should determine the control applied and the interpretation of the control should meet the design intent. For example: Total Runout is typically applied as refinement of form within size limits with location "tagging" along. If refinement of form is not the design intent, position and/or profile should be considered to control the location.
Certified Sr. GD&T Professional
RE: Surface location
mkcski,
What means: ".....the interpretation of the control should meet the design intent......? "
Why not: The interpretation should meet the standard meaning/ definition?
Also, the question is:
if total runout is the design intent and shown on the drawing, then IS the surface location controlled ? (again, the surface location , not the axis location-coaxiality-)?
RE: Surface location
Short answer - total runout does not control the radial location of the surface (assuming that I understand what you mean by "radial location").
One problem here, that Y14.5 perpetuates, is the use of terms such as "location" to describe what is being controlled. As we have found in this thread, the terms "radial location", "axial location", and "surface location" may mean different things to different people.
I have found it very useful to describe constraint in terms of the transformations that are allowed and not allowed. So I would describe a Total Runout tolerance zone in the following way:
-The tolerance zone has perfect form.
-The zone cannot rotate relative to the datums
-The zone cannot translate relative to the datums
-The zone can "progress" (that is, offset away from the nominal surface while keeping the distance between the two boundaries constant)
So the Total Runout tolerance zone in your Surface_location example is two coaxial cylinders 0.02 apart, that are perfectly coaxial to datum axis A. The zone cannot translate or rotate relative to datum axis A. But the zone can progress (the diameter of the two coaxial cylinders is variable - they just have to maintain the radial distance of 0.02). This property is what makes the Total Runout zone not control size. This would be controlled by the 7.780 +.025 -.012 size tolerance.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
Evan,
Look at the attachment. Y14.5 draft
It is stating: “Location of Entire Surface”
I guess the issue is nowhere near to be solved. It is using the word “Location”.
Is the meaning of the total runout going to be changed? Will “finally”/ officially control the “surface location”? I am sure I am missing something, not sure what.
I know your level of expertise and I am sure you can bring this issue to a resolution. What is going on?
Draft states: Where 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.
2009 --see above: gabimot post
My notes:
added: cylindricity
removed: angularity, taper and profile of a surface.
RE: Surface location
Total runout is a control very similar to parallelism and perpendicularity, which also control variation without controlling location.
RE: Surface location
Don't worry - I think that this is just a terminology issue.
I don't think that the meaning of total runout is going to be changed. The descriptions are changed a bit, and rightly so, as some of the previous descriptions were misleading. Total runout never controlled the same thing as angularity, and never controlled the same thing as profile of a surface. So I'm glad to see that those terms are being removed from the description.
There is still the issue of what is meant by the "surface location" of a cylindrical surface relative to a datum axis. Some people would say that this means the location of the center - the "coaxiality" aspect, and total runout controls this. Others would say that surface location relates to the distance from the axis to the surface - the "radial location" aspect, and total runout does not control that. Others might say that surface location relates to where the feature is along the datum axis - the "axial location" aspect, and total runout does not control that either. These are all consequences of the FIM (Full Indicator Movement) definition, where there is no absolute setting for the indicator, only the range of readings matters.
3DDave,
I agree with some of what you said. The absolute radius of a cylindrical surface is not controlled - the radial variation is controlled. The total runout can be verified without knowing the nominal diameter or diameter tolerance - these are independent characteristics.
I wouldn't say that total runout is similar to parallelism or perpendicularity though. There is one special case where total runout would give the same control as perpendicularity - a single planar surface that is nominally perpendicular to the datum axis. But other cases would be different. Total runout allows the tolerance zone to progress/offset, and orientation tolerances allow the tolerance zone to translate. This is not the same thing.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
RE: Surface location
You got me. It's totally different in that when one applies parallelism it requires some other dimensional control to define the limits to the distance to the controlled surface from the given datum reference. Oh. Wait. That's exactly the same description as total runout. So parallelism is to flat things as total runout is to cylindrical things. Which is why I wrote 'similar' and not 'identical,' and further there are cases for perpendicularity that cannot be covered by total runout.
Parallelism vs Total Runout is just a transformation from rectangular to cylindrical coordinate system.
RE: Surface location
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Surface location
I personally like this kind of theoretical discussions. Will force you to “read the letter of the law” (in the actual standard) and I, as individual, learn a lot from those debates.
( Note: Was another debate where we pushed the envelope and has been concluded that the issue was the “definition” (or lack thereof) of the actual local size. http://www.eng-tips.com/viewthread.cfm?qid=391408 )
Going back to the original thread:
Looks like here the issue is the FIM definition.
The question is why even in the new draft the committee does not act decisively and put an end to this controversy and just muddy the water even more by having “location of entire surface”?
Or maybe the interpretation will be that the total runout will control the “location of entire surface”? Is that the intent?
RE: Surface location
If you think that this is discussion far off into the theoretical weeds, you should come to more of our Y14.5.1 meetings ;^).
I defend my hair-splitting in this case. Attention to nit-picking detail is what has made me one of the more successful and wealthy GD&T ... OK, never mind.
3DDave,
You've pointed out an interesting connection that I hadn't thought of before - that parallelism can let distance float in a Cartesian way and total runout can let distance float in a cylindrical way. But I would maintain that total runout and parallelism have more differences than similarities - it isn't just a matter of transforming to a different type of coordinate system.
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
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
I have considered that. The proliferation of specialized symbols for essentially identical cases is of some interest. The ones covered here are various forms of profile tolerance; a zone of defined thickness with or without a defined offset relative to a datum reference.
In the case you mention, the transformation is between flatness of a surface and cylindricity, made by changing the nominal surface curvature from zero to a non-zero finite value. Obviously the committee approached this when they 'unrolled' straightness of a center line to become flatness of a center plane. I don't see a rigorous treatment indicating they looked at it this way, but the effect is there.
RE: Surface location
Does this not mean location?
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
RE: Surface location
Given my level of understanding - more application and interpretation than theory - these "in the weeds" threads are an important learning tool. Please keep it at up!
As understand it, coaxiality controls 4 DOF - 2 translation and 2 rotation, so wouldn't it be better add "and rotation" to the sentence?
Certified Sr. GD&T Professional
RE: Surface location
The answer is yes and no. Again, this is the problem with terms like "location". The tolerance zone is constrained in translation (coaxial) to the datum axis. This means location, but in one sense and not in others. It doesn't mean location in the "radial" sense that some have described. So we can't make a general statement that total runout controls location, or some people may interpret this as meaning that total runout controls the radial location (and thus the size) of the feature.
Personally, I'm not a fan of the "radial location" description. It leads to some odd conclusions, that make things more confusing. One could say that a size tolerance controls the radial location of a cylindrical surface relative to some axis. But I don't think that we want to describe a size tolerance as controlling location. To me, the term "location" in Y14.5 is tied to the idea of translation. If a tolerance zone is allowed to freely translate (as size, form, and orientation zones are), then it doesn't control location.
mkcski,
Yes, I agree that it would be better to add "and rotation" to the sentence. As you say, 2 rotational DOF's are constrained.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
RE: Surface location
May I ask you, if you don't mind, why the runout is not explained, in the standard, in tolerance zone terms instead of FIM, in the same way you stated above?
What would be the advantage of the current explanation " means this" ? Maybe simplicity? Legacy?
Thank you Evan for your entire input on this discussion.
RE: Surface location
FYI The 2015 DRAFT of the next release of Y14.5 has extensive revisions to Runout and eliminated words referring to the type of measuring equipment to be used - like dial indicators and FIM. I have a copy of the DRAFT but it is too much to attach to a post.
Certified Sr. GD&T Professional
RE: Surface location
Runout is NOT included amoung the callouts that control LOCATION.
This Section establishes the principles of tolerances of
location. Included are position, concentricity, and symmetry
used to control the following relationships:
(a) center distance between features of size such as
holes, slots, bosses, and tabs
(b) location of features of size [such as in subpara. (a)
above] as a group, from datum features, such as plane
and cylindrical surfaces
(c) coaxiality of features of size
(d) concentricity or symmetry of features of size—
center distances of correspondingly located feature elements
equally disposed about a datum axis or plane
I mean "directly" control location ( and a new can of worms is opened: What means: directly, indirectly, default, specified otherwise, unless otherwise specified, refinement.........)
RE: Surface location
There is a (implied) relationship between runout and location control in Section 7.6 coaxial Feature Controls - at paragraph 7.6.3 (page 153 in 2009).
Certified Sr. GD&T Professional
RE: Surface location
7.6.3 Runout Tolerance Control
For information on controlling surfaces of revolution,
such as cylinders and cones, relative to a datum axis,
with a runout tolerance, see para. 9.2.
and
9.2 RUNOUT
Runout is a tolerance used to control the functional
relationship of one or more features to a datum axis
established from a datum feature specified at RMB.
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.
7.6 COAXIAL FEATURE CONTROLS
Coaxiality is that condition where the axes of the unrelated
actual mating envelope, axis of the unrelated minimum
material envelope, or median points, as applicable
of one or more surfaces of revolution, are coincident
with a datum axis or another feature axis. The amount of
permissible variation from coaxiality may be expressed
by a variety of means, including a positional tolerance,
a runout tolerance, a concentricity tolerance, or a profile
of a surface tolerance.
At least not to my level of understanding.......For what I understand, so far, the runout is MORE connected/ controlling the axis location/variation, but not the surface location. Am I correct?
RE: Surface location
As mkcski mentioned, the Y14.5 public review draft has tolerance zone descriptions instead of the FIM descriptions.
Why didn't this happen before? You're right that simplicity and legacy were major factors. We studied this a few years ago and came up with some zone-based descriptions to present to Y14.5, and a the time they decided to stick with the indicator descriptions. It turns out that the runout tolerances are very easy to describe and understand in terms of the indicator inspection method, and very difficult to describe and understand in terms of tolerance zones. More so than any other geometric tolerance type. The zones can be odd shapes that are difficult to describe in words, particular for circular runout. Planar slices, cylindrical slices, conical slices, etc. Total runout is easier - the zones are like shells that are the same shape as the nominal feature. The main difficulty is that the FIM concept enables a "progression" transformation that manifests itself differently depending on the feature geometry - for cylinders it's a size-like transformation, for planes it's a translation-like transformation, and for other surfaces of revolution it's a combination of the two. It's bizarre, and non-intuitive for many people.
greenimi,
Try not to read too much into the rough classifications that the GD&T standards use. As you know, most tolerance types control some combination of form, size, orientation, and location. Position is in the Location category, and does control location, but usually controls orientation as well. Orientation tolerances can control form as well as orientation. A profile of a surface tolerance zone can be completely constrained in all aspects relative to a datum reference frame. If this isn't location control, I don't know what is. But profile of a surface is not in the Location category.
So just because runout tolerances are not included in the Tolerances of Location category, this doesn't mean that they don't control location. As you and mkcski pointed out, runout tolerances are mentioned as a coaxial feature control and control the "centering" of the feature. This is because runout tolerance zones are radially symmetric to the datum axis. So they control the "coaxial" aspect of location. But not the "surface location" aspect, as you describe. Again, the classification into form/size/orientation/location becomes somewhat ambiguous when applied to runout tolerances.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
I will not attempt to repeat the extensive postings already made to answer your question: " Am I correct?". But here is my two cents: the issue wiht this thread appears to be the meaning the words - location vs position. The meanings are interchangeable for the average Joe. But in the GDT world, position is one of the location controls. Runout is a composite control that limits form AND location error simultaneously (I'm intentionally not using position here). My recommendation: study position (of the center of a feature) and then get a good grasp of form (shape of the feature's surface). Then see how the two interact with runout, you will then get a clearer picture of why this OP has been going on for days.
When the light comes on, there are other things that will be "obvious". Like: runout applied to surfaces normal to the datum axis control form and orientation (not location). And, if the runout tolerance is less than the feature's size (diameter) tolerance - the size tolerance limits the form error (Rule #1) and the runout tolerance is all location.
Certified Sr. GD&T Professional
RE: Surface location
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
RE: Surface location
I agree that the main issue with this thread is the interpretation of the words. We have seen that "location" can mean different things to different people, and "position" definitely means something different in Y14.5 than in common technical English. They say that the runout tolerances are composite control - but even there, the word "composite" is used in a different way than it is in other sections of Y14.5 (the composite feature control frame, which is something totally different). Also, there may have been a typo in your last post - if the runout tolerance is less than the feature's size tolerance, then the runout tolerance would limit the form error.
John,
That's funny. But you said something that turned out to be incorrect, in good faith, it's not misinformation. If you feel that the discussion changed your understanding, it's gracious of you to say so.
These discussions are sometimes both disheartening and encouraging. On the one hand, if a bunch of GD&T professionals are arguing over whether or not runout controls location, in 2017, then we haven't done a very good job explaining it in the standards. On the other hand, there is a big opportunity to explain it better. I find that at a certain point, the words fail. I tend to revert to mathematical/geometric descriptions, that are much less open to interpretation and can be objectively tested.
Evan Janeshewski
Axymetrix Quality Engineering Inc.
www.axymetrix.ca
RE: Surface location
I'm not saying the arrival at that conclusion was straightforward! Kudos to you guys for fleshing out all the details.
By that same token, we should say that position doesn't control location ... of the surface. But doesn't that sound strange? We all know that position is a "location" control.
So as Evan has point out, it comes down to terminology, and I guess we need to be careful and distinguish between axis location and surface location. This distinction is true for most of the GD&T world.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: Surface location
Yeah, words - written and verbal - are a big "problem" in the world in general, and not just in GDT. Did ya ever consider that a dictionary uses words to define other words. Geez, talk about a spiral of confusion. Then consider the translation errors from one language to another. Then add the vocal and body language that goes with in-person communication. How does the world run at all and come to agreement as to what is being communicated? By careful listening and discussion, which is what we are doing in this forum. Sorry for getting a little philosophical, but I could't help myself.
Certified Sr. GD&T Professional
RE: Surface location
Thanks again, Evan.
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech