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

 

[CheckerHater]

I actually agree with the point that profile should be used to full extent – to do the job that only profile can do.
Unfortunately the trend out there seems to be using profile for everything. It may have something to do with CMM becoming more affordable and widespread.
So if we have to loosen up some of our strict views, then we have to take it simpler: as long as we are able to figure out where the tolerance zone is, the control is legit – no matter profile or runout, or else. That was the point I was trying to make.

 

[Belanger]

I hesitate to jump back in here, but I did finally find the other thread where much of this was hashed out:

http://eng-tips.com/viewthread.cfm?qid=302470

Evan, as I see it (and ref. to the thread above for the blow-by-blow discussion) the only reason that a toleranced diameter is acceptable along with profile on a cone is that the profile tolerance can be adjusted back and forth, thus allowing it to conform to any diameter. This is true if no datum is referenced to locate the zone longitudinally.

Allow me to quote from DeanD3W, who posted this on 17 JUL 2011 (my emphasis added):

"Profile on a cylinder absolutely requires a basic diameter. Profile on a cone requires complete definition by basic dimensions, but if no datum features are referenced that definition may be only the basic included angle of the cone (since the tolerance zone is free to translate in the axial direction it effectively become variable in size). If translation in the axial direction is constrained by a referenced datum feature then a basic dimension to the cone's apex may complete the definition, or as an alternative, a basic diameter combined with a basic dimension to define the axial location of that diameter may be used."

But indeed, the ONE thing we can all agree on is that it would be helpful if the standard gave more direction on this whole aspect of profile.

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

 

[fsincox]

CH,
You are not alone out there! I am just choosing not to rehash old arguments that will only serve to add confusion and leave us all in the same place in the end.
Frank

 

[greenimi]

Well, I can't find that old thread where this issue came up (about using profile on a toleranced diameter), ......"

J-P
You were looking for a thread where ± direct toleranced dimensions and profile combination has been discussed:

I think is this one

http://www.eng-tips.com/viewthread.cfm?qid=320954

You and Dean went back and forth about this issue.

If it's not the thread you are talking about, please disregard my post

 

[waqasmalik]

My understanding is that profile tolerance can be applied both with direct tolerance and basic dimension.The difference will be as follows.
A) With Direct tolerances, profile will lose size control, it will only control orientation and form.
B) With Basic Dimension, profile will control size,orientation and form.

Now the question arises that where to use basic dimensions and where to use direct tolerance.I think Standard has not specified anything like this but i have discussed with one of the expert.According to him:
"Direct tolerances really only work well for individual features of size. If the feature(s) in question ACT like features of size in their application, then dimension them as features of size (i.e. with direct tolerances), but if they ACT like surfaces (i.e. not features of size), then treat them like surfaces and use basic dimensions with profile tolerances.

Now, what do I mean by "Acting" like features of size? Well, does this feature with the plus/minus (direct) tolerances on it fit into a slot on the mating part, or does the mating part always bias this part to one side of this potential feature of size (therefore, NOT acting like a feature of size)"

What u guys think of that?

 

[greenimi]

waqasmalik,

You are taking Mark Foster's statement out of context. He was talking about a rectangular part and about allaround profile+ basic dimensions (or ± direct tolernaced dimensions).
Here in this thread CH , J-P were talking about cylindrical surfaces, conical, --surfaces around an axis-- which IMHO is not the same thing.
You just take a statement from something and extrapolate in something else.
Sorry, I don't think that's the right thing to do.
Anyway, majority of the guys on this form are also on linkedin....so it's easier for them to see the context for the disscusion.

Just my 2 cents

 

[waqasmalik]

we are not reaching to any conclusion so i thought that might help, By the way Mark's This statment was in response of my question.U can check