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Perpendicularity tolerance as refinment of Concentricity tolernce
2

Perpendicularity tolerance as refinment of Concentricity tolernce

Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
Is perpendicularity tolerance is a refinement of concentricity and symmetry tolerance?
To me, perpendicularity tolerance is a refinement of position tolerance, run out and profile of surface.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

If you can create concentricity or symmetry requirement, where tolerance zone is perpendicular to datum axis or plane, then you can use perpendicularity as well.

But I have my doubts.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

In my opinion, if one wants to apply perpendicularity tolerance in addition to existing concentricity or symmetry callout, the value of the perpendicularity tolerance shall not be greater than the value of the concentricity/symmetry tolerance.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

I guess so, but will it create a refinement, as in wrt the same datum(s)?

Imagine perpendicularity to A added to Fig.7-60 or 7-63 in 2009

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

It is not just your opinion, pmarc...winky smile it is just plain common sense that it would be pointless to add a refining tolerance which is larger than the initial tolerance (which would provide the same type of control).

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

If the cylinder that the concentricity contol is relative to has a perpendicularity control, you would have to add the two tolerance zones (which may be larger than your requirements) to determine what perpendicularity control you end up with. Then an additional perpendicularity control would be a refinement. If there is no initial perpendicularity control, adding one would be not be a refinement but an additional control.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Quote (CH)

I guess so, but will it create a refinement, as in wrt the same datum(s)?

I would say this is not "classic" refinement since the two callouts (ASME concentricity and perpendicularity) can't really use the same datum feature references.

But even if we imagine (just for the purpose of theoretical exercise) that in fig. 7-60/2009 right face of the datum cylinder was assigned as datum feature B, and a perpendicularity callout wrt B was applied to the smaller cylinder in addition to the existing concentricity callout, I think that anything more than 0.1 in this perpendicularity tolerance would me meaningless. Futhermore, since the right face (assigned as B) would also have to be controlled by a perpendicularity tolerance to datum axis A in order to avoid incomplete drawing specification, I think the perpendicularity tolerance value for the smaller cylinder wrt B would have to be even less than 0.1 to make any sense.

Besides, why would somebody even want to combine perpendicularity with concentricity in reality? Unless we are in ISO world - then, using my modified version of fig. 7-60, concentricity to |B|A| and perpendicularity to B for the smaller cylinder would work.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
Attached figure has been taken from Alex Krulikowski book of "GDT Fundamentals".
At serial number 6 it is written that perpendicularity tolerance must be refinement of any other geometric control that control perpendicularity of the feature.
Does concentricity control the perpendicularity? With respect to what datum reference?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Waqasmalik,
Concentricity does not control perpendicularity.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
Then how perpendicularity is a refinement of concentricity?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Concentricity is relative to a "parent" cylinder, and perpendicularity would be a refinement relative to that cylinders orientation.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
I am not following.Plz elaborate
Thanku

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Me too.

Also, what about "ISO world"?
I know in ISO concentricity is also named "coaxiality", but I've never heard about ISO allowing features to be coaxial and coperpendicular at the same time.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

You have a cylindrical feature (datum B) perpendicular to datum A (flat surface) to within .010.
You have another cylinder that is concentric to datum A to within Ø.010.
This gives the second cylinder a resulting perpendicularity zone of .020 relative to datum A.
If you need the second cylinder to be controlled more tightly, you add a refining perpendicularity requirement (less than .020).

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
Alex has clearly written that as you can see in the figure i have attached.
"Is the tolerance value a refinement of other geometric tolerances that control the
perpendicularity of the feature?
(e.g Position tolerance, circular run out, total run out, profile of a surface, concentricity, symmetry)"
So concentricity is included amongst those geometric controls that controls perpendicularity.But how?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Quote (ewh)

You have a cylindrical feature (datum B) perpendicular to datum A (flat surface)
You have another cylinder that is concentric to datum A

How that another cylinder is concentric to flat surface?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Got me... that second cylinder should be concentric to datum B, not A.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
Thanx ewh.I was not thinking that way. I would like to ask some more questions.
"Total run out controls perpendicularity" as it is written in the figure attached.
Will the perpendicularity be controlled if i apply a total run out to surface constructed around datum axis?.See figure 9-3 in ASME Y14.5M 2009.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

(OP)
I think total run out will control perpendicularity for the surfaces which are constructed normal to the axis

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

wagasmalik,

I think it is possible to envision a case where a Concentricity tolerance indirectly controls Perpendicularity. Here is a possible scenario:

-Datum feature A is a planar surface
-Datum feature B is a cylindrical surface, nominally perpendicular to datum feature A
-The toleranced feature is a cylindrical surface, nominally coaxial with datum feature B (and hence nominally perpendicular to datum feature A)

The following Concentricity tolerance is applied:

CON|Dia 0.1|A|B|

This tolerance would indirectly control how tilted the toleranced feature's axis could be relative to Datum A (hence indirectly controlling Perpendicularity). I'm not sure if it would be controlled within the same value as the Concentricity tolerance. I haven't thought through the possible scenarios - perhaps others can help here.

Y14.5 does not show an example with a plane/cylinder datum feature combination in the Concentricity section, it just states that there needs to be a datum axis. The plane/cylinder datum feature combination is shown in the runout section, which also states that there needs to be a datum axis. So I don't see a reason why the same datum feature combination couldn't be applied to Concentricity.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Evan,
While I also don't see anything conceptually wrong in |CON|Dia 0.1|A|B|, I am afraid the committee would not be comfortable with it - at least per what para. 7.6.4.1 of Y14.5-2009 states. It the middle of this paragraph it says: "The specified tolerance can only apply on an RFS basis, and the datum reference can only apply on an RMB basis." No "the datum references", just "the datum reference".

CH,
The scenario proposed by Evan would be perfectly legal per ISO (see following link: http://www.eng-tips.com/viewthread.cfm?qid=354287). This is the very same configuration I tried to describe in the last sentence of my reply from 19 Nov 13 15:49. Then applying perpendicularity to A (using Evan's datum features nomenclature) in addition to the concentricity callout would be perfectly legal. You are right though, in ISO this is called "coaxiality" (since it is 3D case), and not "concentricity" (2D case).

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

pmarc,
Given that ISO concentricity/coaxiality is very close mathematically to Position RFS, I agree Evan's set-up will work.

I was more concerned about ewh's example. His post from 11:55 shed some light though. I just still think that in ewh's example specifying larger perpendicularity would not be completely illegal, but definitely useless.
So we can agree that we will have some sort of "quasi-refinement"

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

CH,
I am with you. I think in the ISO world all bets are off! It is a different world! they are just using it to say: "hey the dimension is zero, not missing"
Frank

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Hi All,

What if we omitted the reference to datum feature B, and just kept the reference to planar datum feature A? Like this:

CON|Dia 0.1|A

What do you think of that?

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Even to me your case takes a leep of faith, but my bet is, In the ISO wold it would be fine. Kind of like orientation controlling position (spacing?). I should have done my keyway in ISO!!
Frank

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

That is too much for me, Evan.

Frank, even for ISO that would be too much, I believe. When you take a look at definition of concentricity in ISO 1101, it requires a datum axis.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

pmarc,

I knew it would be too much, but I wondered what reasons people would give as to why. Really, I'm just stirring the muck here.

How about making the toleranced feature datum feature B, and referencing B in the Concentricity FCF? The feature would have to be concentric to its own oriented AME. Technically, the requirement for a datum axis is satisfied.

I'm not suggesting that anyone do this in practice, but I wonder if it violates any rules.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Wait, How about if done in a case like an "interuppted diameter"!! I think we purposefully make these evamples too simple for our purpose, and that the real world is filled with parts that are not that way. It has to work in the real world or it is really useless to us.
Frank

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Evan,
In my opinion making the toleranced feature datum feature B, and referencing B in the Concentricity FCF does not violate any rules.

Frank,
Could you clarify your concern about an "interrupted diameter"? I am afraid I am not following. Thanks.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Frank,

I'm not sure what you mean about the case of an interrupted diameter. Do you mean if Concentricity was applied to a cylindrical surface with an interruption in it? Or something with the <CF> modifier? Or something to do with the datum feature being different if the feature was interrupted (the A-B thing) ? Please clarify.

Evan Janeshewski

Axymetrix Quality Engineering Inc.
www.axymetrix.ca

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Evan,
Sorry, I meant a plain perpendicular datum surfaces referenced concentric with (2) diameters separated by a groove. A situation one might now use "CF", but since ISO, so "CZ" would be more likely.
Frank

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Evan,
I am getting the two threads mixed togeather here, sorry.
Frank

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Hi

Concentricity is not a refinement of perpendicularity, Concentricity controls the centreline of two features relative to each other.
So if you imagine you weld to cylinders together at right angles they could have a perpendicular tolerance but would not need a Concentricity tolerance.

Desertfox

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Actually this thread was about Perpendicularity being a refinement of concentricity, which is (kind of) the other way around.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Gentlemen,

Is it possible that a cylindrical feature could be cylindrical wrt a datum axis established by that datum feature at say MMC,within a controlled tolerance, but still not be perpendicular to a plane, or primary datum A, let's say? So what then would control the perpendicularity of that datum axis to A?

And imagine now that this cylinder further, needs a projected tolerance zone such that it can mate with a plate that has a hole of sufficiently toleranced diameter!

But the mating direction is specified perpendicular to datum A? Do you see a problem with this?

Just asking!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

"cylindrical wrt a datum axis"? Cylindricity never uses datum references.

Could you clarify? I am afraid I am not following you.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

True.

But let's say that the cylinder is a secondary datum feature B. And you only specify a cylindricity for that cylinder surface.

In other words, imagine this cylinder feature is protruding from a flat plate which represents my primary datum A.

What's to say that it doesn't protrude out at some obtuse angel from the plate, which it will do in reality?

There is noting yet that controls the perpendicularity of Datum axis B to Datum A.

Make sense?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

And my other question is - why did you specify a cylindricity, when a total runout might have worked just as well, and it would have been much easier to measure with a simple dial indicator.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Or, you could have simply specified a positional tolerance for the feature, which would have made it far easier to measure with a hard guage!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

As you can see, I prefer easy. I don't like difficult too much!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Cylindricity also is never referenced at MMC.

Quote (asmeY145Manswer)

In other words, imagine this cylinder feature is protruding from a flat plate which represents my primary datum A.
What's to say that it doesn't protrude out at some obtuse angel from the plate, which it will do in reality?
There is noting yet that controls the perpendicularity of Datum axis B to Datum A.

The standard says that datum axis B will be perpendicular to datum A. The perpendicularity of the datum features to each other is either controlled by an appropriate GD&T callout or by the implied 90 rule, NOT by cylindricity. This really has nothing to do with cylindricity so I don't even know why you asked the question.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Wrong, and very wrong!

There is no 'implied rule'. The perpendicularity of datum feature A must still be controlled wrt datum axis B. Your cylindricity requirement does not specify that.

That is why you need the refinement. Because if you never specify how A is related to axis B, then you never control this relationship!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

And remember datum axis B was established by the cylindrical feature. We just happened to call out a cylindricity for it. But we never said how perpendicular it needed to be to datum feature A.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Can you see how it is possible to meet the cylindricity requirement, but still not be perpendicular, as we would like it to be?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

And John,

Thanks for your service! I am just trying to demystify the subject. Hope I can help you!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

In both the 1994 standard and the 2009 standard fundamental rules 1.4(i, and j) clearly define the implied 90 rule. So that means there IS such a rule.

Quote (asmeY145Manswer)

The perpendicularity of datum feature A must still be controlled wrt datum axis B.

This is different from what you originally said. I can agree with this.

Quote (asmeY145Manswer)

Can you see how it is possible to meet the cylindricity requirement, but still not be perpendicular, as we would like it to be?

Of course I can. That was never even in question. I'm not sure where you're getting this idea that I'm somehow confused about it.

Quote (asmeY145Manswer)

Is it possible that a cylindrical feature could be cylindrical wrt a datum axis established by that datum feature at say MMC

As far as demystifying the subject; suggesting examples of cylindricity wrt to a datum and modified at MMC is pretty mysterious in itself.

Hopefully we can all help you. bigsmile

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

New Post powerhound (Mechanical)
4 Dec 13 11:23
In both the 1994 standard and the 2009 standard fundamental rules 1.4(i, and j) clearly define the implied 90 rule. So that means there IS such a rule.

Great!

But only for a theoretical datum reference frame is this true (chapter 4). And that is all very theoretical now. Isn't it. But you still have to relate features to those datums. And you still have to establish datums with features. Points of tangency contact for a primary, for example, two points for a secondary, and so on. So if you never do that, and you just assume on a drawing that your datum features are always 90 degrees perpendicular, well, there is no equipment on the planet, known to man, that can help you to find three orthogonal datums that are 90 degrees to each other, and measure anything against that. This is the real world! So the goal here is only to relate features to one another, not to try and do the impossible!

New Post powerhound (Mechanical)
4 Dec 13 11:23
This is different from what you originally said. I can agree with this.

Thankyou! But read on.

New Post powerhound (Mechanical)
4 Dec 13 11:23
Of course I can. That was never even in question. I'm not sure where you're getting this idea that I'm somehow confused about it.

Well, I started out trying to answer the question that was asked by someone at the start of this thread that asked something like, why did a cylindricity requirement need a perpendicularity refinement, or something to that effect.Right? So yes, that did appear to be in question. Now I am sure that You understand that. Because you have told me so. But.. I just didn't see your correct explanation here on this thread anywhere. And that is the mystery for me tonight!

New Post powerhound (Mechanical)
4 Dec 13 11:23

As far as demystifying the subject; suggesting examples of cylindricity wrt to a datum and modified at MMC is pretty mysterious in itself.

Hopefully we can all help you. bigsmile

And you are probably right. I probably need lots of help for a lot of different reasons. But that's outside of the scope of our discussion! Fair is fair!

See now, you thought I meant something that I didn't mean, and that I said what I meant, and that was what you understood it to mean, and it wasn't meant at all, and it wasn't the way you understood it. And now you have an interpretation problem! My bad! The feature was establishing the datum axis, the cylindricity was not, and that was the problem. Hence my answer to the thread. Got it? And it is necessary sometimes to speak conceptually on this forum, because we are not really looking at drawings, we are only trying to explain concepts.

Interesting, isn't it, how ASME Y14.5M is supposed to communicate clearly a designer's intent? Yet I find there is a lot of confusion out there, even amongst some of the best engineers!

So have you learned anything now tonight? And Relax! How is the weather out there where you are stationed? Stay safe, and please respond. (I don't know how to add a smiley to this thing. Hopefully it works).

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Well it looks like the big misunderstanding is what you were responding to. The original question was if perpendicularity was a refinement of CONCENTRICITY, not cylindricity. This explains what appeared to be an unrelated tangent. I was wondering why cylindricity was suddenly an issue.

Quote:

But only for a theoretical datum reference frame is this true (chapter 4).

The implied 90 rule has nothing to do with any datum reference frame, theoretical or not. Help me understand why you say the implied 90 rule only applies in such a case.

Quote:

So if you never do that, and you just assume on a drawing that your datum features are always 90 degrees perpendicular, well, there is no equipment on the planet, known to man, that can help you to find three orthogonal datums that are 90 degrees to each other, and measure anything against that.

The implied 90 rule uses the default angular tolerance so it's not assumed to be a basic 90. The standard says that a datum reference frame is made up of three mutually perpendicular planes. They are all oriented at a basic 90 degree angle to each other. Datums are perfect, datum features are not. Datum simulators are as close to perfect as possible and we accept that they are close enough to perfect to be considered perfect, even though we know that they really aren't. Parts are checked on surface plates and angle plate every day. Gauge pins are used to check hole diameters and to establish datum axes every day. We do not find datum planes, we establish them with datum features and datum simulators.

Quote:

And you are probably right. I probably need lots of help for a lot of different reasons. But that's outside of the scope of our discussion! Fair is fair!

Your reference to cylindricity at MMC wrt a datum is within the scope of what we're talking about because it's what drew me into the thread to begin with and you seem to be defending your position on it since you are not backing off of it or acknowledging that you were wrong about it. Do you really think this is a GD&T legal callout?

Quote:

See now, you thought I meant something that I didn't mean, and that I said what I meant, and that was what you understood it to mean, and it wasn't meant at all, and it wasn't the way you understood it. And now you have an interpretation problem!

Here's what you said:

Quote:

Is it possible that a cylindrical feature could be cylindrical wrt a datum axis established by that datum feature at say MMC...

"cylindrical wrt a datum axis..." <==this says you think cylindricity can be referenced to a datum.

"at say MMC..." <==this says you think cylindricity can be modified at MMC.

So what is it that I'm misinterpreting...or do you think these things can actually be legally done?

Quote:

Interesting, isn't it, how ASME Y14.5M is supposed to communicate clearly a designer's intent? Yet I find there is a lot of confusion out there, even amongst some of the best engineers!

I can assure you that while I still don't know every single thing in the standard, I'm not the least bit confused about anything you and I have discussed.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

And now just imagine, that you are charged with the task of designing an absolute/ practical absolute guage, just to measure all this nonsense! Where would you start?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

New Post powerhound (Mechanical)
4 Dec 13 23:01
Well it looks like the big misunderstanding is what you were responding to. The original question was if perpendicularity was a refinement of CONCENTRICITY, not cylindricity. This explains what appeared to be an unrelated tangent. I was wondering why cylindricity was suddenly an issue.

I think it is very important to understand the difference between cylindricity, concentricity, coaxiality, circularity, runout, and total runout. The point I was making was simply that total runout is much easier to measure. If you don't need cylindricity (and look at what those things mean in the standard), then why use it, and that is difficult and very expensive to measure. You will need expensive CMM equipment to do that. And it is debatable if that even does the job right. OK? Total Runout can easily be measured with a dial indicator.

Quote:
But only for a theoretical datum reference frame is this true (chapter 4).


The implied 90 rule has nothing to do with any datum reference frame, theoretical or not. Help me understand why you say the implied 90 rule only applies in such a case.

Quote:
So if you never do that, and you just assume on a drawing that your datum features are always 90 degrees perpendicular, well, there is no equipment on the planet, known to man, that can help you to find three orthogonal datums that are 90 degrees to each other, and measure anything against that.


The implied 90 rule uses the default angular tolerance so it's not assumed to be a basic 90. The standard says that a datum reference frame is made up of three mutually perpendicular planes. They are all oriented at a basic 90 degree angle to each other. Datums are perfect, datum features are not. Datum simulators are as close to perfect as possible and we accept that they are close enough to perfect to be considered perfect, even though we know that they really aren't. Parts are checked on surface plates and angle plate every day. Gauge pins are used to check hole diameters and to establish datum axes every day. We do not find datum planes, we establish them with datum features and datum simulators.

Can you do me a favor? Can you read ASME Y14.5 M either 2005, or 2009, Chapter 4, first page to last page, (because they are very different now, MMB as opposed to MMC), and just see, and understand how we establish a Datum Reference Frame. You must do this with features, usually, the features that are most critical to function. Your datums, such as they may be, can only be established by features. And that will never be perfect. But at least now, you can establish the relationship of one to the other within a tolerance, and that can now be directly measured. Right? Now, every other feature on your part will reference those datums that you just established. And they will be related to such, according to whatever tolerance you specify, and can now be similarly measured.

Quote:
And you are probably right. I probably need lots of help for a lot of different reasons. But that's outside of the scope of our discussion! Fair is fair!


Your reference to cylindricity at MMC wrt a datum is within the scope of what we're talking about because it's what drew me into the thread to begin with and you seem to be defending your position on it since you are not backing off of it or acknowledging that you were wrong about it. Do you really think this is a GD&T legal callout?

NO, ABSOLUTELY NOT

Quote:
See now, you thought I meant something that I didn't mean, and that I said what I meant, and that was what you understood it to mean, and it wasn't meant at all, and it wasn't the way you understood it. And now you have an interpretation problem!


Here's what you said:

Quote:
Is it possible that a cylindrical feature could be cylindrical wrt a datum axis established by that datum feature at say MMC...


"cylindrical wrt a datum axis..." <==this says you think cylindricity can be referenced to a datum.

"at say MMC..." <==this says you think cylindricity can be modified at MMC.

So what is it that I'm misinterpreting...or do you think these things can actually be legally done?

NO. Cylindricity is nothing like a positional tolerance. And you are correct about that!

Quote:
Interesting, isn't it, how ASME Y14.5M is supposed to communicate clearly a designer's intent? Yet I find there is a lot of confusion out there, even amongst some of the best engineers!


I can assure you that while I still don't know every single thing in the standard, I'm not the least bit confused about anything you and I have discussed.

That is great news! And I am honored! OK?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

The big red mark in the middle was supposed to say 'NO, ABSOLUTELY NOT'.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

But, Can a cylindrical feature establish a datum axis? Yes. And can a feature control frame somewhere in that drawing reference that datum at say MMC? Now, what does that mean, say you?

Now why can't I just go ahead and refine that feature to be within a cylindricity tolerance (in most cases, I would never do this)? And that actually, has nothing to do with anything I said before. It is totally unrelated.

But it is legal, and, it is also because I determined, that that was important for my design! For some reason! Right?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

The significance of that is when you come to make a guage for it. Sorry folks! I am tired now, but I will explain more tomorrow.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Gentlemen,

I am really confused about the discussion between ASMEy14.5manswer and powerhound.

I don’t take sides, but I am wondering that this discussion has to do with the OP. The OP is probably learning for the GD and T certification test or learning GD an T from AK book for his own edification and he has a question about some statements AK makes in his Fundamental book.

I don’t know why cylindricity shows suddenly up into the conversation, why the total runout is the preferred inspecton method and also why the 90° degress implied angle landed into this mess too.

No wondering why pmarc and Evan (to name a few) bail out from this conversation

I am not drunk or not even tired (not yet on both), but sorry guys I don’t understand………

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Yes, this thread has gone into the weeds a bit.

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Yeah, sorry guys. This has gone too far. I thought it would be a matter quickly resolved with one or two posts. This reminds me of the DrCADD thread from a couple of years back.

I'll bow out and let this thing die.

John Acosta, GDTP S-0731
Engineering Technician
Inventor 2013
Mastercam X6
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

I read DrCADD thread you mentioned. Glad DrCADD didn’t mess up my GD and T training (not his student)

You have to be careful who you are debating/talking to, as you never know when one of his former students might show up one day and dispute some concepts.

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Are you trying to say asmeY145Manswer is DrCADD's student?

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

Sorry folks!

I'm out of it too. And yes it really did end up in the weeds. And that's not constructive.

Better to keep it to one question, and one answer. But it is a complicated subject!

And thank God I don't know any evil Dr CADD. Because if I was his student, then he would have to be a very old man by now.

He was probably the guy that graded me on the quality of my pencil lines, and my stenciled letters. And that was a long time a go - to some of you kids!

RE: Perpendicularity tolerance as refinment of Concentricity tolernce

And if that's the case, then DR CADD must have been a man before his time! Back then you see, we didn't even know what the term CAD meant!

But he did actually show me how to use CAD. That was - drawing a line, and a circle successfully, on an IBM 8086 Personal Computer, and actually running one of the first versions of AutoCad.

Quaint! Isn't it?

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