Circular runout Vs Total runout tolerance 3

[Sa-Ro]

Refer below image

Circular runout should always less than total runout or greater than total runout or equal to total runout?

 

[Sa-Ro]

ok. Thank you.

 

[3DDave]

Yes, he does. If there is no functional requirement or predictable outcome it's another useless argument which does not need to be made. The part does not exist floating in space - it interacts with other parts which produces stresses or motions. In fact, these two features may interact with features on another part and have a huge influence on the ability of combination to function, hence being very dependent on each other.

What does the committee for the Y14.5 standard have to say about wear and contact stress and imposed loads due to unbalanced shafts? Even though those aren't in the Book they still exist as factors to be evaluated. If they are not considered then why have tolerances at all?

 

[Sa-Ro]

Consider the first image.

Dia 50 X 10 mm

Dia 40 X 5 mm

Dia 30 X 50 mm

We are providing rubber sealing in dia 40 and dia 30 with +/- 0.05 mm interference.

Dia 40 will fit into bore dia 40, dia 50 face act as a stopper. Dia 30 projected outside the dia 40 face.

Though I need total runout in dia 40 X 5 mm, the surface available to measure the total runout is small and due to measuring probe size, I have to provide circular runout.

I will provide total runout for dia 30 X 50 - Considerable surface is available for measurement.

 

[Burunduk]

3DDave,
You must have missed the fact that my response was in the context of Sa-Ro saying that he needs to convince the supplier with evidence from the standard that circular runout doesn't have to be smaller than the total runout when the two are applied separately, each to a different feature on the part (different diameters on a stepped shaft). He doesn't have to supply that evidence. The supplier needs to know what they're doing.

How the tolerances are decided on is a whole different issue.

 

[3DDave]

I would like to see a properly drawn assembly section. It appears that datum feature A has no use in this assembly or is secondary to the face of the "stopper" but so far the description is lacking in too many details.

 

[3DDave]

Burunduk - you may have missed that they both have access to the standard and still don't know what it means in terms of performance. Since there is no performance analysis just regurgitating verbatim quotes isn't the solution. If they don't know what the question means, they cannot know what the answer means; in this case the answer to the performance questions as to what is the appropriate datum reference structure and what are the appropriate geometric characteristics.

 

[Burunduk]

As I said in my first reply on this thread:
"it is the requirements of each feature that dictate the tolerance value independently."
Whether the designer makes proper considerations when setting those requirements has nothing to do to the issue the OP is having with his supplier, and those considerations are not what we were asked about.

 

[powerhound]

But my supplier mentioning, total runout will cover circular runout, circularity, concentricity, cylindricity, straightness. Hence even though the circular runout and total runout are specified in different features, total runout should be always more than the circular runout.

Consider having your supplier provide evidence to support their notion. Not the other way around. If I understand this entire case correctly, they are wrong. Circular runout only needs to be smaller than total runout when it is a refinement of total runout, as in applied to the exact same feature. Whether or not what you have described actually meets the design requirement is a different argument. To 3DDave's point, if your drawing is anywhere near to scale, datum feature A as primary is probably not of sufficient size to serve as such.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech

 

[greenimi]

John,

Circular runout only needs to be smaller than total runout when it is a refinement of total runout, as in applied to the exact same feature.

Maybe (just maybe) the supplier is thinking about a general note...such as unless otherwise specified a total runout is applied to all features. (and then the circular runout should be smaller than the general note). I know, a vat of worms will be opened by using this general note for total runout, but anyway, I am tossing it there...

 

[chez311]

Sa-Ro,

Seems like a ridiculous argument to have to make, but if your supplier truly requires evidence look at Y14.5-2009 fig 9-5 (Y14.5-2018 fig 12-10). Circular runout of 0.08 and total runout of 0.05 on different features on the same part.

 

[3DDave]

"it is the requirements of each feature that dictate the tolerance value independently."

Burunduk,

It is the combined interaction of the desired functions of all the features of related parts in an assembly that require an allocation of all tolerances within a system, balanced with the costs and capabilities of suppliers to meet that need and the precision and resources and talent of the inspectors to confirm that result, and especially respecting the limitations imposed by the material properties of all the components involved over the expected environments, operating conditions, and the expected life cycle.

It is apparent the originally posed problem has taken none of these factors into account and that parroting the standard, which does not cover these factors, is not a path to resolution of the conflict.

I will continue to speak for myself to the best of my experience and I do not to answer to your satisfaction.

 

[Sa-Ro]

@Chez311

If I show this drawing to supplier, they will point out, 0.02 tolerance for circular runout and 0.05 tolerance for total runout. Hence circular runout tolerance should be less than total runout tolerance even though it is attached to different features.

I am looking for a drawing where circular runout and total runout are mentioned in different features with circular runout tolerance is equal to or more than total runout tolerance.

Thank you. I got the drawing what I want.

Thank you so much.

 

[3DDave]

Sa-Ro,

It's clear you need a copy of the standard(s) you depend on for your job.

For future reference:

https://www.asme.org/codes-standards/find-codes-standards/y14-5-dimensioning-tolerancing

You can order the 1994, 2009, and 2018 versions from that location.

I am sad that this picture was all that was required - blind faith with no understanding is a terrible way to engineer products.

 

[Sa-Ro]

Sorry, not like.

I fully understood the concept from ASME standard and Burunduk first reply.

But I need a evidence to convince my supplier.

I missed to notice this figure (Y14.5-2009 fig 9-5 & Y14.5-2018 fig 12-10) in standard.

 

[3DDave]

Your supplier has no understanding.

 

[Burunduk]

3DDave,
My use of the word "independently" was not to suggest that when tolerancing a feature it should be isolated as if it's not an integral part of a component that has other features, and not to suggest ignoring that this component goes into an assembly, needs to function in a certain way, etc. Either you don't understand what this is all about or you are taking it out of the context on purpose. I'm glad the OP didn't misunderstand it.

If you read the discussion you could later get the answer to why it was worthy to point out that independence.
Sa-Ro's concern:
"But my supplier mentioning, total runout will cover circular runout, circularity, concentricity, cylindricity, straightness. Hence even though the circular runout and total runout are specified in different features, total runout should be always more than the circular runout."

In short, what needed to be clarified is that a tolerance applied to one feature doesn't control other features. As simple as that. And it's not "parroting the standard" that was suggested. In fact, I mentioned that he will be hard-pressed to find an official statement as an "evidence" to something this obvious but he needs to convey this message anyway in response to what could be the supplier's attempt to influence the specification of tolerances solely for his own convenience (and without regard to functional considerations) under the pretense of following the standard.

 

[powerhound]

Sounds like this one is a wrap but I would recommend in the future when this supplier asks you to prove that you are right, you turn the table and put the onus on them to prove that they are right. This is as backwards as it gets. I've been in this situation before where I see a print with bad GD&T and I'll always have my evidence up front to prove my position before I ask a customer to reconsider their errant spec. I don't go to a customer and tell them to prove their spec is right, before I'm sure that I am.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech