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ASME Y14.5-Next may be better for nubies...

ASME Y14.5-Next may be better for nubies...

ASME Y14.5-Next may be better for nubies...

(OP)
Perhaps some of us come to GD&T with too much baggage. I am hoping that ASME Y14.5-Next will take away some of the redundant symbology and hand out datums only when simultanaity is insufficient. Less is often better, in my opinion. A thread 100 posts long with many very capable minds in turmoil is not something to allow in the next Y14.5. The more nubies we can save from such a grim future, the better.

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Interesting, Peter.  Which symbols are redundant, and I'm not sure that I follow re the datums?
Definitely like to see some simplification, but I fear that the simpler we make things, the less they accommodate the diverse real-world situations we end up discussing here.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

A worthy goal, but I too think that fewer symbols would only result in more debates here!   

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: ASME Y14.5-Next may be better for nubies...

First, I thank the people who did help me with our discussion.

Peter,
I saw your comment in the other thread; I did not want to reply there as I didn't want to hijack it. I must admit I have never understood why people object to the freedom of discussion of relevant issues in public forums? From what I have heard the committee meetings tend to spark the same kind of raucous discussions. Is that kind of fun only to be reserved for the elites? It must be hard putting up with us inferior minds, the Nazis had a solution for that, CH showed me they had a mobile version, too. ;)
I would have welcomed your input since you have all the answers. Did you also bother to notice that I, myself, did not want to handle the issue in the proposed manner, but was basically handed this as a fait accompli. I was just told to vet it, "This is the way inspection wants to do it, is it legal?" typical office politics type of stuff. I have said here before how surprised I am how controversial and political things like GD&T, or going metric, really is when you are the one who is trying to implement it.
I have seen proposals for simplifying GD&T, they were going to unify in 1994 you know, what we got instead is something that looks like ISO but doesn't pass the sniff test, I prefer to judge by the fruits!
I have long thought parallel and perpendicular were unnecessary, that concept went over here like a lead balloon. I would love to see them dump runout for just profile, now that we can officially use it with toleranced dimensions, after all we don't believe in dictating process or inspection methods. It is not the fault of the working engineers that the committee confused the concept of concentricity (TIR) and runout. People wonder how did this issue get confused, simple, they screwed it up. First they tried to hide it by attempting to replace concentricity completely with position in 1982 at that time it became practically redundant. Then after not succeeding in erasing it from the collective memory, by trying to defining it away, telling us it is just so impractical to actually inspect no one would want to do it. Do they really think every point on a surface gets checked, too? Maybe they really aren't as smart as they think they are?
Judging by the fruits of what we actually see in ISO, I personally thank God that foreign engineers are not OK with, "Well the center is in there somewhere" kind of thinking and want to know "how much out of round?" or "how much eccentric?"). Even when they adopted the ISO's idea of specifying a "common zone" for a discontinuous feature they had an opportunity to actually move in the direction of harmonization what did they do, NO, they created "continuous feature", only works with features of size!
There are too many vested special interests that get gouged when they try. Everyone has their own baggage, I have said here before: "what we in the field need is tools to get the job done", if that means more tools so be it, if we don't have the tools to do the job, what good is it anyway.
I hope the next one IS better, I think 2009 is better; I don't think it is simpler.
Frank

RE: ASME Y14.5-Next may be better for nubies...

As Frank seems to understand (perhaps having been involved in voluntary standardization before), there are significant personalities, egos and agendas at play when groups of users get together to reach an agreement on how to do something.  It's not that people want to water down the product, just that consensus is only gained thru negotiation and trade-offs.  Thus, what we as individuals may perceive as bad decisions and worse, are typically the results of trade-offs.  I pushed for a few things and got one or two, but had to support others on their particular focal points.   

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

Jim,
You guys did a good job with 2009, I like it. I do understand how hard it is, congress is the perfect example (no offence intended to you, Jim).  Judging by the lack of ISO books out there they must just use you guys and say "but we do it a little different". I sure would like to see more on metric general tolerancing and independency fleshed out. That is for sure.

Peter,
No offence intended, all my GD&T life I have been told it was simple and found it to be just the opposite, it is simple because they simplify it to teach it, but we have to make it work in the real world.
My real pet-peeve is that you have experts, on this committee, who teach people they don't need to bother to use it. This is just what they all want to hear.  I have seen a guy recommend not to place an orientation tolerance on small short stubby pilots diameters, that are very functional, but are hard to measure or are too short to be measured accurately. This is undercutting the basic concepts we are supposed to believe in basically to make it easier to sell product!  He is not alone, his example is just public, I have seen the other experts talk to my managers and console them. It should be our job to define all the geometry, like the book says. It should be the shops job to decide how and whether to check.
No wonder you get people who think they don't need a position tolerance on a shaft slot. It is because the people who write the principles don't live up to their own words. I suspect the real problems lay a lot closer to home and they are just manifested by the general confusion of the poor people who need to make it work.
 

RE: ASME Y14.5-Next may be better for nubies...

(OP)
Well, once again, I need to apologize to the hard working, individuals who generously offer their advice here. I keep hoping for simple solutions to complex problems. All too often, I fail to see the problem as deeply as is required for a proper solution.  

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Peter,
Do not even think of it anymore; just keep on: "fighting the good fight". I saw your work with profile on castings and the troubles you had with your vendor, I know your pain and I am with you, we need to stick together! I cannot promise blind obedience though!
Frank
 

RE: ASME Y14.5-Next may be better for nubies...

Frank,
You make a good point that design should specify properly and let the shop then decide what to inspect...  I tend to agree, but this brings up a question similar to another current thread...  If you're tolerancing a .030 thick sheet metal part with one planar surface as the primary datum feature and a cylindrical hole as the secondary datum feature, would you apply perpendicularity to that hole?  Theoretically, of course we should, but if we do, isn't it likely that the shop will scoff at our silly spec?

I would like to hear some discussion on this point...  I am very concerned about perceptions and acceptance of GD&T.

I see your point, but I may be one of those you're referring to, or I may be aligned with their approach anyway.

GD&T is the best means by which mechanical design, manufacturing, and inspection can communicate.  Situations can exist, such as very robust designs with very large tolerances, or excellent process control that reliably produces parts that are known to work, where GD&T might be safely avoided (with some risk).  When we apply GD&T doesn't it make sense to use the explicit communication provided to manage the risk of dimensional problems.  Otherwise we need to put a perpendicularity tolerance on a hole punched in .030 sheet metal and run the risk of others viewing GD&T as a cost adder, rather than the profit adder that it needs to be.

Dean
www.d3w-engineering.com
 

RE: ASME Y14.5-Next may be better for nubies...

Dean,
I would love to discuss the implications on flexible parts, let's get that going, probably not in this thread I suppose. I have quite a few irons in the fire right now, so it will take me a while to catch up.
I will try to be good tempered, after all, I don't want to screw up my invitation to lunch! :)
Frank
 

RE: ASME Y14.5-Next may be better for nubies...

Dean,
Please point me to that thread, I agree sheet metal is not well covered in the standard, I myself would have ignored the perpendicularity there. I would like to get in on that and find out what others think and do.
Thanks,
Frank
 

RE: ASME Y14.5-Next may be better for nubies...

Tks Frank, on behalf of the Y14.5 Committee.  I wasn't on the committee, just sat in the back rows as a tolerated pest ... I mean guest.  My first meeting, I raised issue with something (apparently that's not how they've done it, but I didn't know that ;~}  ) and apparently my argument (go figure?!) was effective because the change was made.  Several other changes done that way too, so I was happy.  My "fine" work is part of the Y14.3 and the Y14.41 to be released this year.

And yes, I am one of the buggars who doesn't put an orientation control on a secondary datum fos in thin material wrt the primary datum.  One of the critical factors for me is the legality of the document; if it's on the drawing, then it is enforceable in court.  So, if you put a perpendicularity tolerance of .0005" on a hole in thin sheet, you (as the purchaser) better be able to inspect it accurately & repeatably.  

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

Jim,
I understand compromise must be made and you are not in the business of making enemies and I do not want to make one of you, either.

There lies the fundamental issue, is it our job to define the required part geometry, or only what can be inspected and where? Here or anywhere? Change the rules then, don't say these are the rules and then don't follow them! Say it only applies to machined parts not sheet metal, or something! I bet part of the problem is independency makes much more sense for sheet metal parts. The ISO acknowledges different tolerances for different production processes and they have independency.
Frank
 

RE: ASME Y14.5-Next may be better for nubies...

Frank,
I think we should apply GD&T explicitly and specifically to the more important features in the views of a drawing, with a profile in an "unless otherwise specified" general note for the features or characteristics deemed not critical enough for their own tolerance specs...

That profile in a general note is the key to enabling only the sensible tolerance specs to go on a drawing.  The requirement that "dimensioning and tolerancing shall be complete" is still met, but the drawing much more efficiently enables managing risk.  A benefit of this approach is that inspection will only address the explicit and specifically applied tolerances, so no one should scoff at any impractical or unmeasurable (insufficiently repeatable) specs.  The profile in a general note, with a relatively large tolerance value, serves ensure that "complete" specs are provided and also that no one needs to pay for parts with large, unexpected issues.

If there's a better approach, then I'm all ears.

Dean
www.d3w-engineering.com
 

RE: ASME Y14.5-Next may be better for nubies...

Frank,
I don't take offense about contrary opinions; they may confuse me, but I don't take offense at them.  I rather like hearing how other people interpret things and process things so that I have something else to contrast my thoughts against.  I even, occasionally, change my mind on something!  

There apparently was a sheet metal standard years ago, but there was not enough interest/participation to keep updating it, so it was removed (the ASME rules require that every standard be reviewed and revised, re-affirmed, or removed every 4 years).  I had several clients a couple years ago that wanted ASME to do something again, but none were willing to participate.  I offered to lead such a group and only 2 or 3 people stepped forward, and they couldn't commit at the time either.  If people want it, they need to commit to it, that means manpower, time and travel for a good 4 years in many cases.  As an FYI for anyone interested, note that such endeavors MUST be made under the auspices of a recognized organization such as ASME or you risk anti-trust issues (something else that scares people off).   

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

(OP)
Why would you not use profile of a surface for holes in sheet metal? It would eliminate the theoretical possibility of oval holes without adding the hard-to-measure perpendicularity control.

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Dean,
I love it, I wrote a company book espousing such a thing 1993, I was a little more naïve then and thought it was revolutionary, my company's response was to  proceeded to ban profile tolerancing completely!
It is basically what I am advancing in this thread:
thread1103-315749: Simple plate
I then started toying with the idea of combining a general profile note,  to an ISO "IT" tolerance grade, defined to a "MASTER FRAMEWORK". That started me on my current journey of study and interest in the ISO system of general tolerancing as I see it to be very similar in concept.
Frank

RE: ASME Y14.5-Next may be better for nubies...

Jim, if you choose to not use an orientation tolerance on a secondary datum feature, how shall we simulate it (assume it's referenced at MMB) to create the DRF?

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: ASME Y14.5-Next may be better for nubies...

Well, J-P, I'm apparently missing something in your question.  If you reference the secondary datum feature at MMB, then you put in a simulator pin at the MMB condition with zero perpendicularity error ... because that's effectively what you have on a thin stock situation; zero perpendicularity error.  I used to believe that you had to follow the "control the datum feature" edict blindly, but then the reality of thin material situations smacked me around a bit.  In MOST metrology environments, there's no way they are going to be able to have enough truly cylindrical wall to establish a tilt on the axis (there is tapering at the one end and often bulging at the other).  Where then is the practical application and function of a perpendicularity control in that situation?  
Now that is NOT an absolute; one client was using a pressed-in optical element in a sheet metal component; the material still wasn't substantial, but because of the physics, the perpendicularity of the axis (well, the cylindrical wall really) was critical.  They had a means of inspecting that shallow hole for orientation.   

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

But that's just it, Jim.  I don't propose a perp tol on a hole through the thin part because it is something that's checkable. I would propose it because it defines the gage.

A zero perpendicularity tolerance is assumed in your condition. Why build a gage based on an assumption? Make the tolerance zero at MMC; that's effectively what you are saying. It would not be checked as you say (i.e., axis), because as that datum gets simulated, it will automatically be checked by that envelope.

Rule #1 relates size to form, but not size to orientation.  So the practical application and function of a perpendicularity control of zero in that situation is that it merely "crosses the T and dots the i," so to speak.

Now, after all that:  I don't mean to sound too pushy on this point -- I am not really a cheerleader for this. I just don't want people to think that there is no logic behind having perpendicularity on a paper-thin part.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
http://www.gdtseminars.com

RE: ASME Y14.5-Next may be better for nubies...

Fair enough, J-P.  Unfortunately I've tended to not use 0(M) as much as I could/should have because too few people understand it; arguably a poor reason, but a reality that we all live with.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

I think we all understand the theory; we all don't use it as much as we should. That is directly related to the issue here, the screaming shop. It also makes the point that those of us who do understand it, know it is an education problem not a tolerancing problem. Just like my issues with RFS or MMC on threads, they want MMC, when I say just put a fastener in it and measure it, No they don't want to take the trouble to do that either, but, it is right in the book and generally what we want!
Frank
 

RE: ASME Y14.5-Next may be better for nubies...

(OP)
I get what you guys are saying with the 0(M)perpendicularity. Nevertheless, I find the concept of composite profile tolerancing to be more straightforward. I doubt that nubies would get the idea of 0(M)perpendicularity quicker. I do understand that using 0(M)perpendicularity facilitates bonus tolerance.  

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Peter,
Do you mean to apply as an "all around" thing, or just the holes. Isn't part of the problem the implication of prefection the envelope principle trys to invoke also?
Frank

RE: ASME Y14.5-Next may be better for nubies...

(OP)
I am refering to using a composite profile tolerance for the holes, Frank. If simultanaity is not sufficient to orient the holes with respect to to top and bottom of thin sheet material, then make one side of the sheet Datum A and orient the hole to it in one or more fcfs.

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Peter,
You won't get any argument from me about using Profile in this scenario.  The shop ... well, that's another story.

On the topic of 0(M), though, education is, indeed, the issue.  Depending on the group, I teach it different ways.  I often show one of our training slides with 0(M) on it and go ... "well that's not right, is it!...Or is it?  What are they asking for here?", and then lead them thru the exercise.  Gets'em every time, doesn't matter if it's design, shop or inspection (and even management gets it too!!!).  After that, they're converts.  Problem still arises when I don't have the entire food chain in my classes ... bogs down when one of the groups is missing.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

Peter,
As a flat sheet or as formed?
Frank

RE: ASME Y14.5-Next may be better for nubies...

(OP)
At the moment, I was thinking of a constrained-to-a-flat profile. (Possibly constrained by gravity, if we are talking about a film.) In the case of formed sheets, spelling out orientation with a datum structure (if rigid) and/or notes limiting a datum to a perimeter around the hole pattern (if flat, but flexible) could be required.

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Does the standard need to be simpler, or does the training and certification environment need adjusting?

I've long wondered if there should be another lower level of GD&T certification, not one that focuses on esoteric aspects or trick questions... but one that covers the typical day to day basics.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: ASME Y14.5-Next may be better for nubies...

(OP)
Jim,

Do you think that my example would be a problem for shops mainly due to a lack of the tools needed to inspect parts or mainly due to their lack of understanding of the profile callouts?

Ken,

My last week of GD&T training (2010) pushed profile tolerancing very hard. Some of the students were in college and barely even had blueprint reading skills. By the end of the training, they seemed to fully comprehend composite profile applications with and without datum structures. So it seems to me that some of the other methods, such as 0 (M), get in the way of what seems to me to be a better, comprehensive way to bring new students up to speed.

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Peter,
The problem is composite of both issues.  What I've seen too often is that shop doesn't have the ability / knowledge to check a profile tolerance because they have never been trained adequately, or more specifically because some instructor told them it requires a big expensive CMM.  I've taught people how to do open setup inspections for exactly this sort of thing without issue.  Also taught them how to do it with a CMM, with an optical comparator, with a vision system, ... you get the idea.

I find that college/university students seem to accept the material easily enough, but few understand what it means in the "real world" of metal, plastic, etc.  Another example of "theory is great, but what what do I do with it".

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

Jim,
  A few posts back you mentioned that if you specify a tolerance on a drawing then you should be able to measure it. Are you saying that legally, as in court, it is incumbent upon the customer to prove that a part is NOT to spec as opposed to the supplier proving that a part IS to spec?

  If that's the case then some people here where I work are really going to have to re-evaluate how they spec parts. These guys regularly tolerance parts to values that we cannot verify such as a cylindricity tolerance of .001 mm.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: ASME Y14.5-Next may be better for nubies...

(OP)
Maybe. A prosecuting attorney may show you a drawing and ask you what the drawing means and how you verified that the product met the spec's. If Jim is working for the prosecuting attorney, you may be in trouble. You might show why the need to meet it is not relevant, but you might still look incompetent and compromise the outcome. Of course, 0 (M) is not the same as +/- zero, but you would need Frank to stand up to Jim. I think that .001 mm cylindricity would not look good in court unless your measurement uncertainty and bias compensation are accurate and reproducible...

Peter Truitt
Minnesota

RE: ASME Y14.5-Next may be better for nubies...

Interesting question, Powerhound.  If I understand the judicial process correctly, the claimant (customer, assuming they are suing over bad parts; supplier if they are suing for payment for parts) would have to establish that they have a legitimate case as a first step.  A situation of point/counter-point, I think.  So, if the customer is suing, then they'd have to prove that the parts don't meet their spec.  If the supplier is suing, then they'd have to prove that they do meet spec.

As Peter indicates, it's GDTP-S's & P.Eng's (P.E.'s)that tend to be called as expert witnesses to determine the meaning of the print and whether or not something is inspectable by nature of the geometries, materials, and whatever other factors.

Jim Sykes, P.Eng, GDTP-S
Profile Services  www.profileservices.ca
TecEase, Inc.  www.tec-ease.com

RE: ASME Y14.5-Next may be better for nubies...

(OP)
In a liability case, be prepared to defend the drawing, design, traceability, and quality of fabrication.

Peter Truitt
Minnesota

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