Total Runout on a Cone 3

[Belanger]

I suspect this topic has been covered here before, but I'll toss it out there again.
Does anyone have a problem with total runout applied to a tapered cylinder? I claim that it's OK, as long as the angle of taper relative to the datum axis is given as a basic dimension.
Some folks try to say that it's not allowed since it's not in the standard, but this forum has discussed how the standard gives basic principles but can't show every possibility.
May be fodder for Y14.5-Next.

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

http://www.gdtseminars.com

 

[fsincox]

J-P,
I am thinking of a conventional runout set-up on a sine plate? Thus the basic angle? I am not an inspector and nor do I play one on TV, but if it is reasonable that it could be done like that, I say yes. Particularlly because runout seems more focused on an inspection process than on real geometric definition.
Frank

 

[TheTick]

Just... NO. How are you going to control the angle and axial position while measuring?

 

[Belanger]

Tick ... huh? The purpose of total runout IS to control the angle and axial position (and form/orientation).
It would be the same dial indicator setup as regular total runout, except the rail that the indicator slides on would be at a prescribed angle other than 0º from the datum.

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

http://www.gdtseminars.com

 

[powerhound]

While I agree that the standard cannot show every possible scenario that could occur in the field; I feel that there was ample opportunity to have at least one illustration that showed the use of total runout on a taper. The fact is that there are several illustrations of runout on a taper and every single one of them is circular. Even figure 6-50 in the 94 standard shows both types of runout in the same drawing and they switched to circular on the tapered portion of the part when they didn't have to. The curved part was showing circular just fine. Figures 6-47 and 6-48 show both types of runout and they switched part geometry between illustrations just so circular runout was shown on a tapered cone. They didn't have to do that. They could have used the same part, without the tapered portion, to illustrate circular runout, right?

It is my belief that total runout was not intended to control angles other than 0 and 90 but it is only for the reasons previously stated.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
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[MechNorth]

J-P, I've postulated the same thing and discussed it with a few people (Evan, I think we discussed this at one of the meetings?) I envisioned it being inspected just as Frank described above.
The value of it, however, is questionable because ... wait for it ... it's the same as ... wait for it ... SURFACE PROFILE!

For curiosity's sake, how would you even indicate that you wanted the control applied at the angle rather than typical cylindrical? That's the shortcoming of the total runout approach on a cone, whereas a profile control ... well, it's somewhat intuitive, and gets the same result.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[Belanger]

Jim, it's not the same as profile because profile also controls size of the cone. Runout does not, because the diameter must still be a ± tolerance. (I thought for sure you would agree with this as an "extension of principles.")

Why is it so mysterious to indicate that the control applies at an angle other than parallel?
See attached graphic.

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

http://www.gdtseminars.com

 

[axym]

J-P,

I don't have a problem applying Total Runout to a tapered cylinder. Or any surface of revolution, for that matter. Circular Runout is already applied to these geometries, and there is no fundamental reason why Total Runout cannot be. There are definitely practical difficulties, especially if one wants to use the traditional indicator method of inspection. Tracking an indicator properly through an angled or curved path is more difficult than the usual parallel or perpendicular geometries. If a digital inspection method is used to compare measured points to a tolerance zone, the extra difficulty is less.

powerhound,

I agree that the issue of Total Runout on cones and curved surfaces of revolution was deliberately avoided in '94 and '09. But I would say that say that these applications will probably be in the next version of Y14.5.

Jim, I don't think Total Runout on a cone is the same as Surface Profile. I know that the standard shows an example that tries to make it the same, but I have a big problem with that example ;^). It's Fig. 8-18 in 2009, 6-24 in '94. Surface Profile is applied to a conical surface, in conjunction with a directly toleranced dimension. The Surface Profile tolerance controls the form, orientation, and location of the cone. To me, the appropriate characteristic for that application would be Total Runout, and not a mutated version of Surface Profile. That figure is one of my biggest pet peeves with Y14.5. I dislike the whole idea of mixing directly toleranced dimensions with Surface Profile anyway. It's very case-specific and not rigorously defined.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[fsincox]

I am happy to say, I think, I can agree with you both. Runout is not my “thing” so I am choosing to believe J-P that it makes some sense to actually inspect as we have earlier described. Given that, it just seems an easy call to me. I do want make clear, I am not actually one who believes that runout must be inspected a certain way, I believe it is only necessary that if you could actually do it, it would pass. Or to put another way, even though it is, by definition an inspection method, you really only need to believe it would pass if it could be rotated and inspected that way. I take this from the standard’s self stated emphasis on defining controls and not dictating process.
I have had the opportunity to review 2009’s section 8.2 on profile recently, I would interpret the last paragraph, stating it may be used as a refinement of toleranced dimensions as an opening to allow it to replace runout anywhere. I have hinted at this in a few threads here recently and have picked up hints that Jim realizes it too.
Recent threads have questioned the uses for datums in profile of a line (an obvious replacement for circular runout come to my mind. There was a recent use of a profile on the surface of a discontinuous spline ID, where it was combined with a toleranced dimension, (I decided not to say anything as it was noted, specifically, under 1994 standard). The question was posed in the same thread of: “would it add to the tolerance”, that is also answered in that paragraph for us. It does not, it is treated as a refinement of the size. That is exactly as I would have expected it should be.
Frank

 

[Belanger]

Frank, I wouldn't be ready to go that far. The sentence you see about profile being a refinement of toleranced dimensions refers only to toleranced dimensions relative to a datum. The actual profile itself cannot be toleranced because the early part of paragraph 8.2 says that profile must be applied to a "true profile."
But I like your take on the philosophy based on inspection and how the function is the important driver.


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

http://www.gdtseminars.com

 

[MechNorth]

Evan, that the standard (Fig. 8-18, '09) shows what I'm talking about, IMO means that it is the correct interpretation/ understanding ... doesn't it? That is the legal definition, not my preference. As to the difficulty of inspecting at a basic angle to the axis, it can add setup error if open-setup is used without a dedicated/purpose-built fixture at the prescribed setup. Other than that, I don't see an issue. BTW, I don't like the use of the tolerance on the cone either; much better to use a basic dimension & profile.

As Frank suggested, I look at Total & Circular Runouts as being special cases of profile controls (surface & line), for surfaces parallel to and normal to the datum axis.

J-P, I'm looking at your graphic but in no way does it communicate that the indicator is to be normal to the nominal geometry; how, then, would a less experienced reader know that you intend for the basic angle to guide them to that thought? At the very least, you would need a note such as "AT 15 DEG BASIC ANGLE".

There may be some support for the use of total runout on a conical surface in "9.4.2.1 Applied to Surfaces Around an Axis" ... "...total runout may be used to control cumulative variations such as circularity, straightness, coaxiality, angularity, taper, and profile of a surface." Of course there is no guidance of how to achieve this, but it puts the toe in the door. Unfortunately they don't support it in the graphics anywhere; they only show circular runout on tapers. Then, however, section "9.5 Application" does not indicate total runout as applicable to conical or other non-parallel/non-perpendicular surfaces wrt the datum axis.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[Belanger]

Jim, my drawing doesn't have to communicate that the indicator is normal to the surface, because ...wait for it ... the standard says it! (Couldn't resist.)

Paragraph 9.4.2: "When verifying total runout, the indicator is fixed in orientation normal to and translates along the toleranced surface."

So again, my point is that we all accept total runout on a cylinder and accept that the indicator moves along at an angle of 0º to the datum. If I prescribe a different angle, why should the world suddenly fall apart?

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

http://www.gdtseminars.com

 

[MechNorth]

Tks for the schooling. And no reason, just not what people are used to.

Revisiting your graphic, I don't see support for the angle being specified as basic used with the total runout. The book shows profile control with a basic angle (Fig 8-17 & -18), and circular runout with a toleranced angle (Fig 9-2).

Expanding upon your extension of principles, for a mathematically-definable geometry (curve on Fig 9-5), do you then mean total runout could be used on such a definable surface as long as the indicator is able to follow the nominal profile, as long as some cross-section on the nominal geometry is defined with a +/- tolerance? The standard does read "surface", without restricting it to cylindrical, planar or conical. I'm asking because I had not thought of overwhelming value in using total runout beyond the planar/cylindrical surfaces of revolution about a datum axis. Your extension, however, extends the "acceptability" to far more surfaces of revolution.



Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[CheckerHater]

I'm with J-P here.
If you look at Fig.9-2 and Fig.9-3 (2009); both specify exactly the same: indicator to be held "normal to the true geometric shape"
Sadly, the Standard lacks the definition of "true geometric shape", but definitions for both "true position" and "true profile" say they are defined by basic dimensions; so one doesn't have to extend principles too far to assume that basic angle will describe "true shape". I would consider it "safe bet" at least.

 

[axym]

I'm going to put something out that represents my current understanding of Total Runout, based on working on zone-based definitions for the runout characteristics. Here goes:

In terms of tolerance zone mechanics, Total Runout is identical to Surface Profile in all but one respect. Total Runout allows the tolerance zone to "offset" away from the true profile and Surface Profile does not. This is analogous to reading the indicator's TIR as opposed to an absolute reading.

The offsetting of the tolerance zone manifests itself in different ways for different considered feature geometry. For cylindrical features, the offsetting is purely radial and mimics (but is not quite the same as) letting size float. For single planar surfaces, the offsetting is purely axial and mimics (but is not quite the same as) letting location float. For cones and surfaces of revolution, the offsetting is a more complex combination of radial and axial and doesn't really mimic anything.

Total Runout is distinct from Surface Profile in other ways, which are Y14.5 restrictions and aren't directly related to the tolerance zone mechanics. Total Runout requires the presence of a datum axis, and the geometry of the considered feature is confined to certain types. Cylindrical surfaces that are nominally coaxial to the datum axis, planar surfaces that are nominally perpendicular to the datum axis, and (arguably) cones and other surfaces of revolution. Surface Profile can be applied to a surface of any nominal geometry. In principle, Total Runout could be applied without a datum axis (or any datum features at all) and to other types of irregular surfaces. But these applications would be very far removed from the traditional indicator-based roots of the characteristic, and Y14.5 has not explored them as yet.

I fully expect vigorous opposition from some of you, as some of this goes beyond or conflicts with current Y14.5 explanations.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[MechNorth]

Evan, if it goes against Y14.5, then how is it acceptable? You're saying "It's not legal, but it's legal"...what? Sorry, but I'm not following your point here.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com

 

[ptruitt]

Even if 'Total Runout' on a cone is somehow acceptable, Evan, what does the extension of the concept bring to design intent that 'Profile of a Surface' does not offer? I hope that Y14.5-Next focuses on logical and entirely comprehensible extensions of 'Profile of a Surface' such as cones, unless there are designs that somehow require this other methodology which seems to me to be unnecessarily complex, especially to new users. Perhaps I am missing something. Is this a design-intent discussion or a dial-indicator discussion? (No insult to dial indicators or their operators, intended).

Peter Truitt
Minnesota

 

[pmarc]

Just a thought...
Why couldn't the definitions of runouts (circular or total) say that readings must be taken in a direction perpendicular to a datum axis for surfaces of revolution or parallel to a datum axis for surfaces at right angles unless otherwise stated? Wouldn't it reflect funtional requirements of runout applications - rotating elements - better? Wouldn't it solve all the problems with runout of cones and any other fancy sine shapes?

 

[CheckerHater]

what does the extension of the concept bring to design intent that 'Profile of a Surface' does not offer?

How about ability to actually measure the part without buying CMM?

 

[MechNorth]

CH, why would you need a CMM to check profile of a revolved surface? Though possible cumbersome or complex to setup, an indicator on defined guideway(s) would work just fine for revolved surfaces. Of course in a volume application, an automated edge-projection system establishes runout very nicely, and would eliminate complex setups.

Jim Sykes, P.Eng, GDTP-S
Profile Services

http://www.profileservices.ca

TecEase, Inc.

http://www.tec-ease.com