Y14.5.1 Public Review Draft 1

[axym]

Hi All,

A new revision of ASME Y14.5.1 Mathematical Definition of Dimensioning and Tolerancing Principles is nearing completion. Y14.5.1 is an important standard in quality assurance and metrology as it defines actual values for geometric characteristics. The new revision supports ASME Y14.5-2009 and contains significant developments in datum stabilization and actual values for profile tolerances.

You can order a free hard copy of the public review draft from ASME at the following link:

Link

We are looking forward to feedback from GD&T users in industry. Comments are encouraged and will be accepted by ASME until Feb 19, 2019.

Let me know if there are any questions and I will be glad to help.


Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[chez311]

Evan,

Thanks for the update! I've been wondering when we might expect a new update to the math standard, I guess this is why I haven't seen you around here much, I'm sure most of your extra time has gone to this - I'll definitely be checking this out, but since I'm just starting to familiarize myself with the current version of Y14.5.1 it will probably be mostly for my own edification. Do you know when it is expected to have a finalized version released - will it be sometime later this year?

 

[3DDave]

I should be happy for this heads up, but it actually does the opposite. 25 years since the first attempt, for a document supporting a soon-to-be replaced 10 year old version, leaving a 7 day working window in the remaining few days seems practically hostile to the idea of a public review.

 

[axym]

3DDave,

Sorry to hear that you're not happy. Full disclosure - the public review draft has actually been available since Dec 19. I'm just late in announcing it on the forum.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[axym]

chez311,

I'm cautiously optimistic that it will be released sometime later this year - hopefully in the 3rd quarter or so.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

I should be happy for this heads up, but it actually does the opposite. 25 years since the first attempt, for a document supporting a soon-to-be replaced 10 year old version, leaving a 7 day working window in the remaining few days seems practically hostile to the idea of a public review.

There is always this website

https://cstools.asme.org/csconnect/PublicReviewPage.cfm

where one can find all drafts under public review. Y14.5.1 is at the very end of 3rd page.

 

[3DDave]

pmarc,

I would have checked that over how much time in the last 25 years on the off chance that there was an update?

To maximize the chances, that's once a week, 52 * 25 * 3 minutes to scroll through all the possible release notes. That's a full 2.7 days of checking, break it into 8 hour sections and that's more than a solid full-time week to that one task.

This forum is clearly known to many members of the ASME committees and there have been no communications prior to this.

I'm reminded of this:

“But the plans were on display…”
“On display? I eventually had to go down to the cellar to find them.”
“That’s the display department.”
“With a flashlight.”
“Ah, well, the lights had probably gone.”
“So had the stairs.”
“But look, you found the notice, didn’t you?”
“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of the Leopard."

Douglas Adams, Hitchhiker's Guide to the Galaxy.

Evan - does it support my interpretation of the real virtual condition represented in '2009 figure 4-16(c) and not the blind adding of numbers depicted? I guess you cannot tell anything about anything involved with the development. It's too bad that discussion notes have never been published to allow everyone else to understand what was intended.

 

[pmarc]

3DDave,
I didn't mean to say that visiting the website each week is a perfect way to check if new drafts are available. It is not, but at least there is something we can use to track that information down. In fact, I think much better option would be availability of some kind of 'Subscribe' button on that website that would allow people to receive an email notification each time a new draft has been published for a review.

As for why this (or similar) functionality hasn't been be added to the website yet... well, I have my theory, but I will not say it out loud.

 

[3DDave]

pmarc,

I would guess based on the number of users on this forum who are not committee members and also didn't mention that the draft notice was out that the chances of it's being discovered are close to, if not identical to, zero.

The ASME Y14 committee has my name associated with three other drafts, including one they charged a good deal of money for, and could have e-mailed a notification if they were interested in participation. It is clear that is not the case.

I am also disappointed that, yet again, they will not publish the comments as they are received, an action that would likely save a great deal of duplicated effort and time and allow the focus on better resolutions to discovered problems. Publishing comments is what most other language developers seem to do when inviting public comment.

 

[pylfrm]

We are looking forward to feedback from GD&T users in industry. Comments are encouraged and will be accepted by ASME until Feb 19, 2019.

Let me know if there are any questions and I will be glad to help.

[ol 1]
[li]Is this the first public review draft of ASME Y14.5.1-20XX?[/li]
[li]Are additional public review drafts planned?[/li]
[li]The page you linked says "Some proposals are also available electronically, directly from this page for no cost". Why is this one not?[/li]
[li]Have any comments been received so far?[/li]
[li]For position tolerances, do you expect this revision will continue to include the incorrect interpretations (surface for RFS, resolved geometry for MMC and LMC) along with the correct ones (resolved geometry for RFS, surface for MMC and LMC)?[/li]
[/ol]
If answers to any of these questions are readily available online, I'd be interested to know where.


pylfrm

 

[axym]

3DDave,

You're right, I'm not at liberty to discuss details. But I can say that the tolerance zone, boundary, and DRF definitions in Y14.5-2009 are followed as much as possible. A large part of the scope of Y14.5.1 is to enable calculation of actual values from these definitions.

pylfrm,

1. This is the first public review draft of Y14.5.1-20XX.
2. Additional public review drafts would depend on what revisions need to be performed after the first one. For comparison, the recently relesed Y14.5-2018 had one public review cycle.
3. Issuing of electronic versions versus hard copy versions is an ASME decision - I don't have information on this.
4. I don't know what comments have been received so far - I will see the list after the comment period is over.
5. See the response to 3DDave's question above. Y14.5-2009 contains an axis interpretation for position tolerances at MMC - why is this considered an incorrect interpretation?

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[3DDave]

Evan,
Please see the discussion from

https://www.eng-tips.com/viewthread.cfm?qid=447050

18 Dec 18 08:26

The axis interpretation is fine. The concept of what transformation applies when a different DRF is created is not.

 

[looslib]

It seems a little late to be reviewing a proposed Y14.5.1-20XX against the Y14-5-2009 standard when you look at the ASME website and see that Y14-5-2018 is scheduled for release with a month!

Shouldn't this Y14.5.1 be against the latest Y14.5?


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[pylfrm]

axym,

Thanks for the answers.

Here's my attempt at an answer to your question:

In certain cases of extreme form deviation (within limits of size) or orientation deviation of the hole, the tolerance in terms of the axis may not be exactly equivalent to the tolerance in terms of the surface. See Fig. 7-6. In such cases, the surface interpretation shall take precedence.

I would say that the tolerance in terms of the axis is never equivalent to the tolerance in terms of the surface, simply because the definitions are completely different. I suspect the intended meaning would be conveyed better if 'tolerance' were replaced with 'calculated actual value', so this is probably just an issue of semantics.

However, it seems to me that the calculated actual value in terms of the axis is almost never exactly equivalent to the calculated actual value in terms of the surface. The two definitions have very little in common, so if they both happen to produce the same result for a particular feature, it's basically just a coincidence. The surface interpretation is always correct by definition, so the axis interpretation is, in general, not.


pylfrm

 

[chez311]

Evan,

Is it alright to discuss here details about the latest draft? Since this review is free and public I'm going to assume thats not an issue but I'd like to check first. I just received my copy.

 

[axym]

Ben,

Yes, I agree that it would be better if the latest revision of Y14.5.1 was coordinated with the latest revision of Y14.5. We've been in catch-up mode for a while and still are, and it was decided that there was still value in issuing a math definitions standard to support Y14.5-2009. Drawings referencing the 2009 standard will still be around for quite a while, and it usually takes a few years for new Y14.5 revisions to move into common use. But the timing of the releases is an unfortunate coincidence, with our public review draft out at the same time that Y14.5-2018 is published (the PDF version is already available on the ASME website, and the print version will be available Feb 21). I wish that the schedule had been different, but this was beyond our control. I can say that we learned a lot from the last development cycle, and I am confident that the lag time for Y14.5.1 revisions will keep getting shorter.

pylfrm,

I think I agree with everything you said about position tolerances at MMC. The surface interpretation and axis interpretation control different pieces of geometry, and do not get equivalent results. Y14.5 portrays them as essentially equivalent, and has for a long time. This could be considered a first-order approximation - it works well in cases where the form and orientation variation of the feature is relatively small (and not so well if these are relatively large). In Y14.5-1966 the interpretations were described as "different, but compatible". To me, the axis interpretation is a conservative estimate of the clearance fit condition at the surface. The surface geometry of the feature is parameterized in terms of the size and center location of its actual mating envelope, which makes it much easier to evaluate the feature with open setup methods and CMM's and calculate a measured value of position. Even if the surface interpretation represents the "correct" answer for a clearance fit, the axis interpretation is defined in Y14.5 and therefore must be included in Y14.5.1.

chez311,

What we can discuss probably depends on what the details are. Perhaps you can contact me directly first.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pylfrm]

the axis interpretation is defined in Y14.5 and therefore must be included in Y14.5.1.

Fair enough. At least the Y14.5.1 draft agrees with Y14.5-2009 that the surface interpretation takes precedence for MMC and LMC.

For RFS, Y14.5-2009 only provides an axis interpretation. The Y14.5.1 draft also provides a surface interpretation and says it takes precedence, which seems strange given the claimed goal of supporting Y14.5-2009. What's the story there?

An argument could be made for the interpretations that get superseded to be moved to a nonmandatory appendix, but I don't imagine that's very likely to happen.

The surface geometry of the feature is parameterized in terms of the size and center location of its actual mating envelope, which makes it much easier to evaluate the feature with open setup methods and CMM's and calculate a measured value of position.

Assume we have a pattern of holes with a MMC position tolerance applied, and we have obtained a suitable sample of points on the surface of each using a CMM. To determine the measured value with the surface interpretation, we can calculate the distance from each point to its corresponding true position axis and find the minimum. This is quite straightforward if the DRF is fully constrained. To determine the measured value with the axis interpretation, we must first find the UAME for each hole. This is substantially less straightforward algorithm-wise.

What am I missing?

pylfrm

 

[axym]

pylfrm,

I see your point about precedence of the surface and axis interpretations. This will be examined if a comment is submitted - I encourage you to do that.

I agree with you about determining measured values with the surface interpretation using a CMM - from a calculation point of view it's really quite straightforward. It's just that CMM software packages generally don't have this feature - their calculations are based on the axis interpretation. The programmer needs to create a custom calculation. I expect that this will change in the future.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[chez311]

Evan,

My question about the draft that I was really wanting to discuss was exactly along the lines of pylfrm's regarding RFS calculation of surface interpretation despite there being no mention of it in Y14.5-2009. I was a bit hesitant after your initial response to continue down that line of inquiry but really my question was very general - and in fact could apply to the current Y14.5.1-1994 as from what I understand surface interpretation was not valid per Y14.5-1994 either.

In fact soon before you posted this announcement, pylfrm and I were discussing this very topic in another thread (

https://www.eng-tips.com/viewthread.cfm?qid=448113)

- the timing of which is almost uncanny! I'd be very interested to hear your thoughts on the matter in that thread, as we were discussing the merits and functionality of the existing RFS surface interpretation calculation, irrespective of whether it was actually allowable per Y14.5 - my initial take was that there doesn't seem to be much use to it and I did not understand how it related to the feature functionally, but pylfrm has of his latest post put forward some interesting points which I am still considering.

 

[3DDave]

I would recommend that the next time a Draft goes out with a watermark that everyone involved gets some training about how they are supposed to work. They should not be used for random redactions.