Total runout 3

[illini8181]

I have a question about total runout. My understanding is that total runout controls form, orientation and location, but not size. However, Section 9.4.2.1 of ASME Y14.5-2009 states that "Where applied to surfaces, constructed around a datum axis, total runout may be used ot control cumulative variations such as circularity, straightness, coaxiality, angularity, taper and profile of a surface." What confuses me is that this section says total runout controls profile of a surface. Doesn't profile of a surface control size?

Thanks

 

[Belanger]

A great question. I don't really agree with that part of the statement. This is because profile of a surface must be applied to a true profile (meaning that the diameter would have to be basic). Yet, runout can't be applied to a basic diameter, so it lacks one of the foundational requirements of profile. (A rare exception to profile requiring a basic diameter is a cone where no perpendicular datum is given.)

I prefer to think of it this way: profile is actually one tier above runout, in terms of a GD&T hierarchy. Therefore, we can say that profile of a surface on a cylinder will control total runout, but I disagree when they say that total runout controls profile of a surface.

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

 

[pmarc]

Yet, runout can't be applied to a basic diameter...

Not true J-P. See fig. 8-26 in '09. And in the light of that figure runout seems to control true profile of a surface.
Although I agree with you that profile is one tier above runout

 

[Belanger]

Pmarc -- those basic dims are for the profile tolerance, not the runout tolerance.
So while you're correct in terms of "the letter of the law," I stand by my statement because the runout itself is on a "floatable" diameter constrained by the 0.25 profile.

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

 

[pmarc]

Okay, I agree that runout tolerance itself (without additional profile control) can't be applied to a contour dimensioned by basic dimensions only.

 

[CheckerHater]

The standard doesn’t say “runout controls all the possible cases of profile”.
Profile can be specified without datum and act in the way similar to flatness or cylindricity.
In this case it may be indirectly controlled by total runout.

 

[IRstuff]

Is 8-27 (2009) the same as 6-17 (1994)? Something that looks like a rocket nozzle?

Seems to me that in that figure, the profile tolerance of 0.25 is a basic accuracy requirement, i.e., the surface could be anywhere within the ±0.25 boundaries and could potentially vary within a given part by that much. So, one could imagine a profile that zigzags between those boundaries and still meet the profile tolerance. The runout requirement seems to say that wherever the profile starts in the profile boundaries for a given part, the profile cannot move by more than ±0.15 closer to either boundary, thereby actually controlling the shape of the profile.

TTFN
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[Belanger]

CH -- to say that runout controls profile implies that runout controls at least the main constitutive elements of profile. Even if profile lacks a datum reference on the cylinder, it still inherently controls size. So I think it's not quite correct to say that runout controls profile when applied to a cylinder.

It's like saying that flatness on a surface controls parallelism. Sure, flatness controls ONE element of parallelism (form), but such a statement is an overreach.

IRstuff -- Yes, the figures are the same, and I would agree with your statements. Profile can trump runout, but runout doesn't trump profile.

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

 

[CheckerHater]

8-27 actually shows Runout, not the Total Runout.

And it basically means that any circular cross-section cannot "wiggle" more than 0.15, while the entire profile may vary within 0.25

 

[waqasmalik]

JP
How profile inherently controls size if it lacks datum reference?
Ref Fig 8-8,page 163 of ASME 2009.

 

[Belanger]

waqasmalik -- Because in the example you cite, and also in the examples that the original question was referring to, the profile tolerance continues around the entire part. So if the profile appears on both sides of an opposing size dimension, then the profile tolerance inherently controls the size.
So for Fig. 8-8, ask yourself what the maximum length would be. The basic length is 60 mm, but with the profile wrapped around the part (actually, all over the part), then the maximum permissible length would be 60.6 mm (0.3 mm outward on all sides).
Notice that all of this has nothing to do with a datum; it's the same surface being toleranced everywhere.

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

 

[illini8181]

Thanks for the help everyone. I am running into an issue where everyone in my group is interpreting a total runout tolerance on a taper as a profile. I am convinced that the size of the taper is separately controlled by two toleranced diameters (looser than the runout). However, everyone in my group thinks that the runout tolerance is the size tolerance on the part.

I was wondering, is it possible to "officially" email the ASME committee with questions and receive official responses? I'm just curious, because I am a new member to the group, and so no one will take my word for it, and also most of the older guys in the group wouldn't put any stock in anything on internet forums. So it'd be great to get an "official" answer to my question.

Either way, thanks everyone for the help!

 

[Belanger]

Yes you can propose suggestions to the secretary of the Y14.5 committee, but I don't know if they have an email. See the attached graphic, which is a snippet from the front of the standard that explains how to contact them.

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

 

[waqasmalik]

thanx JP
We must intimate ASME committe regarding this statement written in 9.4.2.1 of ASME 2009.What do u think?

 

[CheckerHater]

Intimate?

 

[IRstuff]

"to tell people something in an indirect way
intimate that: He intimated that he intends to leave."

TTFN
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[waqasmalik]

i meant that should'nt we convey this to ASME Committee that Run out does not control profile of surface.Its the profile which control run out

 

[CheckerHater]

Gentlemen, if you care to look at ASME Y14.5-2009 Fig.8-17 you will see profile that doesn’t control size.
What exactly is preventing us from using runout the same way?

 

[Belanger]

CH -- you've found the one exception that I mentioned in my first post (see above). I will try to dig up an old thread about this.
At any rate, the paragraph in question (9.4.2.1) is talking about total runout, which is presumably applied to a cylinder, not a cone. Thus the diameter must be a basic dimension.

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

 

[CheckerHater]

John-Paul,

Just look at Para. 8.4.4 Conicity"
"A profile tolerance may be specified to control the conicity of a surface in two ways: as an independent control of form as in fig. 8-17, or as combinations of size, form, orientation, and location, as in Fig. 8-18."

It's all right there in black and white: conicity, not cylindricity, two ways, one with controlling size and one without controlling size.

Denial much?