GD&T tolerancing of a cone using multiple segments frame
GD&T tolerancing of a cone using multiple segments frame
(OP)
Hello everyone!
I am new to this forum though I spent nearly a year learning from valuable discussions around here.
For cones, I usually stick to a single profile tolerance but this time more control is required to better describe the functionality of the part.
Attached is a sketch of what we are thinking of doing and we are really concerned by how this would be interpreted by other people.
Basically we want the cone surface to be in maximum possible contact with his mating partner so we apply an 0.1 form tol (N°007). The axial position of the cone in respect to the datum A is not that important thus the profile tol of 1 to datum A (N°008). To finish the cone axis should be closely coaxial to the datum B and perpendicular to datum A hence the position tolerance(N°009).
Now a couple of questions:
1- Does the multiple segment frame shown in the sketch reflect the requirements described above?
2- Does the application of fig 8.18 - 2009 standard in this scenerio make sense? Should diameter DIA_5 (N°017) be based on the possible variation due to profile tol N°007 or profile tol N°008 instead?
3- is there a risk that the association of profile with position is interpreted as per fig 8.24 - 2009 standard?
4- The cyl dia is a simplification of a set of features that need to be controlled relative to the cone. Can we use the cone as secondary datum for those features?
Sorry for the long post. Any suggestions is welcome, thanks in advance.
2JL
I am new to this forum though I spent nearly a year learning from valuable discussions around here.
For cones, I usually stick to a single profile tolerance but this time more control is required to better describe the functionality of the part.
Attached is a sketch of what we are thinking of doing and we are really concerned by how this would be interpreted by other people.
Basically we want the cone surface to be in maximum possible contact with his mating partner so we apply an 0.1 form tol (N°007). The axial position of the cone in respect to the datum A is not that important thus the profile tol of 1 to datum A (N°008). To finish the cone axis should be closely coaxial to the datum B and perpendicular to datum A hence the position tolerance(N°009).
Now a couple of questions:
1- Does the multiple segment frame shown in the sketch reflect the requirements described above?
2- Does the application of fig 8.18 - 2009 standard in this scenerio make sense? Should diameter DIA_5 (N°017) be based on the possible variation due to profile tol N°007 or profile tol N°008 instead?
3- is there a risk that the association of profile with position is interpreted as per fig 8.24 - 2009 standard?
4- The cyl dia is a simplification of a set of features that need to be controlled relative to the cone. Can we use the cone as secondary datum for those features?
Sorry for the long post. Any suggestions is welcome, thanks in advance.
2JL





RE: GD&T tolerancing of a cone using multiple segments frame
That profile call-out does not control the axial position of the cone in respect to the datum A... their relationship (cone axis and Datum A) to each other is perpendicularity (not position)... however, with that profile call-out you control the distance of the cone from the Datum A.
RE: GD&T tolerancing of a cone using multiple segments frame
Use composite profile
PLTZF profile xxx to A primary and B secondary (locate the cone)
FRTZF xxx to A primary (refine the orientation to A)
If you need a third segment could be added (with no datum)to refine the form of the cone
RE: GD&T tolerancing of a cone using multiple segments frame
The conical control in this case is to control the cone concentric to datum axis B, so the primary datum would be datum feature B (which is more logic than the planar datum feature A), and I will choose datum feature B as primary datum on both position and profile DRF (datum reference frame).
I will use multiple single segment profile control to control the separate requirements, the upper segment is a profile of a surface control, it controls size, location, and orientation relative to the datum reference frame; in this case, the profile of a surface control limits the size and location of the surface of the cone. The lower segment is a profile of a line control, it controls the line elements for form and orientation relative to datum axis B, this zone floats within the 1.0 tolerance zone. The purpose of the profile of line here is to refine the form and/or orientation of line elements of the cone surface. Please ref to the attached file for details. And I will not use the position to control the cone location since profile (both profile of line and surface) already control the location of the cone.
That’s my two cents, please let me know if I am wrong.
Season
RE: GD&T tolerancing of a cone using multiple segments frame
I have a couple of questions for you and for the OP
#1: What is the advantage of using profile of a line instead of a profile of a surface?
#2: How do you know that B is primary in the assembly versus A as shown in the OP drawing? How do you know what is the physical reality of this assembly? Is B acting like primary when the parts are put together or maybe A is the one orienting the part (as originally shown)?
I do understand that you WANT (would like) to control the orientation to B, but the question is how the physical reality would look like.
I agree: Dia_5 should be basic. I also agree to not use position to control the cone location.
And by the way, I am not saying you are wrong. I am trying to learn what would be the difference between these callouts and when would you use one versus the other.
RE: GD&T tolerancing of a cone using multiple segments frame
Greenimi: " Make DIA_5 basic"
SeesonLee: "Profile of a surface can be applied to conical part but need the basic dimension to define the conical shape, so Dia_5±e need to be a basic dimension, and the size of the cone will be toleranced by the profile control"
You both agree that DIA_5 should be basic but it isn't what is proposed by fig 8.17 and 8.18 (2009 standard). Isn't this dimension is an indirect way to control where the cone starts or ends? (At least this is what I always thought).
Seesonlee:
#1. As you, I am not really sure about profile of line. I don't think that controlling line elements is necessary.
#2. A should stay primary (without the context B seems to make more sense).
To all: What I get from your answers is that the position tolerance is not required since the coaxiality requirement to datum B can be conveyed by a profile tolerance. Now I can't use a composite tolerance since the datum sequence in the lower segment will not match the upper segment, see the attached sketch.
2JL
Sorry for the time it took to answer. English isn't my first language.
RE: GD&T tolerancing of a cone using multiple segments frame
The definition of profile is that it be applied to a "true profile" -- that is, one where the contour itself is pre-defined by basic dimensions. So a cone should have a basic diameter.
In Figure 8-17, I would say that they're OK, however, because there is no datum at the end of the cone to stabilize where a cone-shaped profile tolerance should be. In other words, you can have a tolerance zone of the correct angle superimposed over a part, and slide the zone left or right until it finds a best fit over the actual part until it finds the diameter, which of course still needs to be within the ± range.
But in my humble opinion, Figure 8-18 is not really correct, simply because they do have a datum B which serves to locate the cone-shaped zone in a left-right manner. So the diameter should have been basic -- there is no possibility of sliding the tolerance zone left or right to overlay the actual cone.
Where are Evan or Dean when I need them?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
Until this day I accepted the standard the way it is mostly because I thought it was defining the gauge plane as used in stack-up analysis.
2JL
RE: GD&T tolerancing of a cone using multiple segments frame
I’m not quite sure the application and the design intent, so it’s just based on my assumption, but from your latest gage sketch, I am still thinking you want to control the cone concentric to datum axis B, that’s why I will choose datum feature B as primary datum.
As for further consideration, profile of line will only control the line elements of the cone surface, if changing to composite profile of surface tolerance, it will control the straightness and roundness of the cone surface, probably this will more reflect your application, and how do you guys think? Please ref to the attached file.
Season
RE: GD&T tolerancing of a cone using multiple segments frame
Why A as a secondary in the FRTZF? What is the value of it? What degrees of freedom A is stopping (what degrees of freedom that haven't been stopped by A and allowed to be stopped according to the composite rules)
RE: GD&T tolerancing of a cone using multiple segments frame
Here is a good example (from Genium) and it will answer your questions.
CODE --> greenimi
Season
RE: GD&T tolerancing of a cone using multiple segments frame
Actually your example didn't answer my questions and in my opinion that example, from Genium, is wrong --as shown--
Why?
Because --as other people around GD and T word stated before --other threads or discussions---- reference to B (in Genium example) adds no geometrical value--
From Mark Foster
""The datum references in the FRTZF are only allowed to stop *rotational* degrees of freedom. There are no rotational degrees of freedom that B can stop that A hasn't already stopped. Therefore, the B secondary in the FRTZF adds nothing to the callout -- at least theoretically. If datum feature A were somehow unstable (a "rocker") or were referenced at MMB or LMB, then there may be some added "help" from B secondary in stopping those 2 rotational degrees of freedom, but technically we should not be "overriding" the A primary.
My comment was coming from the "Theory-to-reality" perspective. I agree with you wholeheartedly that the B secondary in the FRTZF is not allowed to override any of the degrees of freedom (rotational, since that is all that the datum references of the FRTZF are ever allowed to stop) that A primary has already stopped. However, in the real world, *IF* datum feature A were an "unstable" or "mobile" datum feature, and in reality not doing a good job of stopping those rotational degrees of freedom, then if a physical datum feature simulator were present for B, it may, in fact, do a little biasing of the part and "help" to stop those rotational degrees of freedom.
Having said all that, since, in theory, B should not be allowed to stop any rotational degrees of freedom, and therefore, in theory, B as a secondary in the FRTZF does nothing, then, in practice, one should not have called it out there in the first place.""" (Mark Foster---Applied Geometrics--)
RE: GD&T tolerancing of a cone using multiple segments frame
I was shocked to know the example from Genium is wrong, it’s the first time I know that someone pointed out the mistake on Genium’s tips. I will contact with Genium to understand the right way to call out the datum reference frame.
Well, for the OP questions, I would like to know the other comments and/or suggestions.
Season
RE: GD&T tolerancing of a cone using multiple segments frame
Pmarc, where are you when I need your help?:)
I don’t know if I can “survive” without your help, please......
RE: GD&T tolerancing of a cone using multiple segments frame
This is the sort of ambiguity that Y14.5 cautions against. All the cone dimensions that control the taper and location should be basic.
RE: GD&T tolerancing of a cone using multiple segments frame
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
I'd prefer if the dimensions along an axis were taken from the intersection point, which has no size and will always be the place that exactly aligns with a mating taper.
In any case this means that only the taper angle dimensions the taper. Where it starts and ends are dimensions of those features.
RE: GD&T tolerancing of a cone using multiple segments frame
Without datum B, I agree that the size could be toleranced because we wouldn't have anything to anchor the profile tolerance in the left/right direction.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
FRTZF never locates (only orients) and that's why B is not needed (does not add any geometrical value if it is added on FRTZF)
Just my opinion.
RE: GD&T tolerancing of a cone using multiple segments frame
RE: GD&T tolerancing of a cone using multiple segments frame
If you don't mind... let's focus on Figure 8-18 of the standard. It's kind of the same thing, but not composite. I've always had an issue with that one so that's why I'm asking you. Please read my post above from 16:26 on Feb. 23 and let me know your feedback.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
RE: GD&T tolerancing of a cone using multiple segments frame
I have some questions for you, if you don’t mind:
1. In my opinion, the picture attached by SeasonLee from Genium is a better representation, or more robust definition of the cone--Profile Tolerancing of a Conical Feature, Datum Related--, than fig 8-18 (shown in the standard Y14.5-2009). Do you agree? If not, why?
2. In the same token (Genium picture), do you agree, that datum feature B, used as SECONDARY in FRTZF (AGAIN, secondary in FRTZF) is useless (has NO geometrical value)
Thank you
RE: GD&T tolerancing of a cone using multiple segments frame
First, I'll keep beating my same drum that both pictures are flawed, because they are not applying profile of a surface to a "true profile," which is a foundational rule of that symbol. The diameter of the cone (24 mm or .700) should be basic.
That said, they are the same except that the Genium example has a refinement to the profile -- the FTRZF. I don't know if I'd call it better, but it is more specific if the function requires such a fine-tuning.
For your second question, yes the addition of datum B in the FRTZF seems to be useless. This is because the primary datum A will have constrained 4 degrees of freedom. The 2 degrees not controlled by A would be rotation (irrelevant to what we're doing on the cone) and left/right translation of the entire part -- and this too is irrelevant because by definition the .005 number is only controlling the cone's orientation to the FTRZF's datums (as well as size and form of the cone itself).
IOW, if the cone translates left or right a little bit (that's what datum B would be looking for) then such a movement can only be controlled by the upper PLTZF.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
First, I'll keep beating my same drum that both pictures are flawed, because they are not applying profile of a surface to a "true profile," which is a foundational rule of that symbol. The diameter of the cone (24 mm or .700) should be basic.
I agree. 24mm (standard picture Fig 8.18) and .700 (Genium) should be basic.
That's exactly what I have said regarding the picture from OP (Make DIA_5 basic)--see my initial post-- 22 Feb 15 12:20
Thank you.
RE: GD&T tolerancing of a cone using multiple segments frame
For what it's worth, I would like to share some thoughts with you about some of the topics being discussed here:
1. In Genium example does B in the lower segment of composite profile callout add any value?
In my opinion it does not. Any rotational degree of freedom that B is able to constrain, has been already constrained by A.
2. Should dia. 24 in fig. 8-18 be basic?
I will take a risk and say that it depends on what characteristics of the cone one wants to control. In most cases it should be basic, but I believe there are situations where basic diameter will not work.
To elaborate a little bit more on this, per current scheme shown in fig. 8-18 profile tolerance controls axial and radial location of the cone relative to datums A and B, orientation of the cone to these datums, and form of the cone. However, it does not control size of the cone. In other words, profile tolerance zone (which is a space between two coaxial conical boundaries) is not fixed in radial size - it can grow and shrink depending on actual size of the circular element located at basic 18 from datum plane B.
Now, what will happen if we change the dia. 24+/-0.2 to basic? We will never be able to accomplish the same effect, because profile tolerance zone (regardless of whether defined by single segment callout, or by composite) will always be fixed in size, thus will never be able to grow and shrink.
3. Has the answer to the original question been provided?
I would say no, because none of the proposed solutions seems to fully capture the functional intent as described at the very beginning. 3 things that need to be addressed are:
- form of the cone to be within 0.1;
- the axial position of the cone in respect to the datum A to be within 1;
- the cone axis to be coaxial to datum B and perpendicular to datum A within 0.05.
Assuming that these requirements are trully functional and that datum features precedence has been thoroughly considered, first thing I have to say is that I don't see a way to decode these requirements using profile tolerance(s) only. If it is okay to keep form of the cone within 0.1, then there is no chance to control position of the cone to B within 0.05 using profile, and not to override the 0.1 form requirement. Something else must be used.
Having said that, my idea would be following:
(a) to leave the DIA._2 as is, if it is acceptable to have size of the cone within [DIA._2 minus e - DIA.2 plus e] limits, OR to change the DIA._2 to basic, if size of the cone can be controlled through 0.1 profile tolerance;
(b) to apply composite profile tolerance to the cone:
- in upper segment |1|A|B| - to control location and orientation of the cone to datums A and B within 1;
- in lower segment just |0.1| - to control form (and size, depending on choice in (a));
(c) (and this is the trickiest part) in order to refine location of the cone axis to B and orientation of the axis to A, to define two additional gage planes close to each end of the cone, apply two diametrical dimensions at these planes without specifing diameter values, and attach two position feature control frames, |pos|dia. 0.05|A|B|, to these dimensions.
What do you think? Would it work?
RE: GD&T tolerancing of a cone using multiple segments frame
I agree that changing the diameter to be basic will give a different effect, but a more direct question is if it's even legal to have a toleranced diameter.
For instance, take Fig. 5-12. If I change the symbol to profile of a surface, would that be legal? If not, then why is a cone any different (as long as it has one end of the part stabilized as a locating datum)?
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
I knew we will get to this
I think this may be a little bit surprising for you, but in my opinion in fig. 5-12 profile with no datum references would be legal. It would do the same thing as cylindricity, but I would not use it exactly because there is much more direct way to express my intent - and that is the cylindricity tolerance.
RE: GD&T tolerancing of a cone using multiple segments frame
About the tolerance dimension (again!), because I was aware that it could be in conflict with the profile tolerance, I had always make sure the tolerance value (e) was derived from the profile tolerance as you can see in the attached sketch. Yeeh! No need to do that anymore! Why is there such a thing in the standard at the first place?
Link
Pmarc,
Does the second sketch reflected what you suggested in 3.c? I am not quite sure how well it will work. Since the two additional controls will only apply at the defined locations and not to the entire axis of the cone, the part could be well in spec for these locations but not elsewhere.
Link
2JL
RE: GD&T tolerancing of a cone using multiple segments frame
So to illustrate my point, please see the attached graphic. Based on your reply about Fig. 5-12, then you would have no problem with making the diameter of 20 in my first sketch into a ± tolerance. Similarly, you should be willing to allow each of the other pictures to have a ± tolerance on the diameter rather than basic. (Remember, we're talking about what's legal, not what is wise.)
Yet would it really be legal to have the R42 in the last picture be toleranced rather than basic? I think I hear you saying yes, which was the cause for my surprise. (Or if you say no, then the question becomes why the last picture is different from the first.)
Sorry if this seems like a side-track to everyone, but answering this issue in my mind is very integral to the original question regarding how to dimension a cone when a profile tolerance is desired.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
If the definitions were properly made there would be no need for flatness or cylindricity. These are forms of profile control which only require the subject profile to lie within two boundaries of given shape, which may have a specific scale associated or not. Runout is similarly a subset of profile.
As far as the poor definitions in Y14.5 are concerned, anything is legal. Y14.5 has been a do-it-yourself kit for a long time. This is seen in the interpretation of figure 8-18, which contradicts the method of interpreting other datum reference frames.
RE: GD&T tolerancing of a cone using multiple segments frame
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
Yes, you would have no problem with making the diameter of 20 in your first sketch into a ± tolerance (although, like I already said, profile would not be my first choice there), however I do not see a ± toleranced radii working on other sketches. It is simply because ± tolerances applied to radii like these are not standardized/recommended tools, thus open for different intepretations.
2JL,
You are correct, position of the axis (I would actually call it the derived median line) of the cone would be controlled within dia. 0.05 only at the gage planes - I should have mentioned that in my previous reply. In other locations the "axis" would be indirectly controlled by profile 0.1 with no datum references.
One way to have closer control over location of the axis of the cone (if you think this could be an issue) would be to use more gage planes.
I am also thinking about getting rid of all gage planes and associating position FCF with basic angular dimension. But then I would prepare for many questions, because such method is not explicitly shown in the standard.
RE: GD&T tolerancing of a cone using multiple segments frame
My question is what advantages will bring this new method (position FCF associated with basic angular dimension) of tolerancing the cones?
Probably then (with position), MMC’s can be used (if it is functional) , right?
Can we gage these cones, by the end of the day? How many gages? One? Multiple? Or we have to still resort to the CMM for proper inspection?
Thank you
RE: GD&T tolerancing of a cone using multiple segments frame
"Yes, I would have no problem with making the diameter of 20 in your first sketch into a ± tolerance (although, like I already said, profile would not be my first choice there), however I do not see a ± toleranced radii working on other sketches. It is simply because ± tolerances applied to radii like these are not standardized/recommended tools, thus open for different intepretations."
The reason I came up with the idea of position FCF associated with basic angle was to have location control of the axis of the cone separated from profile controls in order to satisfy quite unique functional requirements. In general case I think the technique could use MMC's in order to employ surface interpretation of the callout and make verification with hard gage possible, but in this specific situation I don't think the gage would verify these functional requirements properly - we know that the cone may float in location within 1.0 relative to A, and this is not what the gage would verify. I was rather thinking about sole axis/DML position wrt A|B control, thus applied RFS.
RE: GD&T tolerancing of a cone using multiple segments frame
Now we're at the crux of it. I don't see how it is logically possible to say that a simple arc needs to have a basic radius for a profile tolerance, but when it becomes a full circle (cylinder/cone) it would suddenly be OK to give the radius/diameter a ± tolerance.
Profile may be used in conjunction with ± tol in terms of relating the surface back to a datum. But I think the curvature of the surface itself cannot get a ± tolerance.
Comments still welcome, but thanks for hearing me out, everyone...
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: GD&T tolerancing of a cone using multiple segments frame
I am not saying that a simple arc needs to have basic radius because profile tolerance is used. I am saying it needs to have basic radius because the standard does not offer any other unambiguous way to control size of the arc than a marriage of basic radius and profile tolerance. Radius with ± tolerance, unlike ± toleranced diameter, is vague specification, thus subject to different interpretations.
Also, I did not say that for full cylinder/circle/cone radius with ± tolerance would be OK. It wouldn't, again, because the standard does not tell us how to deal with that kind of animal.
If you do not feel comfortable with profile tolerance applied to a circle/cylinder/cone with ± diameter tolerance and you do not see any reason for it, let's use slightly different/more complicated scenario, if you don't mind:
Imagine two parts - one having hexagonal hole, the other with hexagonal pin. The hole and pin are locationally controlled relative to some other datum features. Main functional concern is not only to make assembly of both hexes possible, but also to keep uniform (within a tolerance) gap between both features all around. In other words, it actually does not matter how big/small the hexes are (of course within certain limits) as long as both hexes are precisely controlled for their form and location. How would you encode that requirement using GD&T language?
RE: GD&T tolerancing of a cone using multiple segments frame
However, I am still not convinced that isn't some sort of conflict between certain statements provided. I know you answered this, but still I cannot wrap my head around it. My brain is not firing up all its cylinders or is not wired properly.
I need more practice (reading it-re-reading it)
RE: GD&T tolerancing of a cone using multiple segments frame
More particularly you are looking at a scaling problem - but that only applies to regular hexagons; other 6 sided convex shapes, irregular hexagons, are not scale variants of each other. There needs to be a symbol for regular hexagons to have a symbolic control based on that shape.
So a note: This pin/hole shall conform to the smallest enclosing/largest expanding right-prismatic surface of a regular hexagon within x.yyyy units as measured normal to each corresponding face. The axis of symmetry of the shape shall be located within a diameter of t.ssss units of the true position. The dimension across the flats of the surface shall be f.gggg+/-j.llll units.
RE: GD&T tolerancing of a cone using multiple segments frame
Regarding the hex situation, I'm not sure how I would have done it before I read the various suggestions. I think my main inclination would be the same as Dave's: when in doubt, there's nothing wrong with still using a note to describe a specific requirement.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems