Here is the scenerio. The tolerance block on my customer's drawing is +/- .010.
The dimension in question is .460min

What is your interpretation?

How can there be a tolerance of +/- .010 when they only require a minimum? :confused:

Here is the scenerio. The tolerance block on my customer's drawing is +/- .010.
The dimension in question is .460min

What is your interpretation?

Does the block tolerance have the disclaimer, "Unless otherwise noted"? If it does, there's your answer--the "min" callout supersedes the block tolerance. If not, I would still say that specifying "min" without an associated "max" leaves the door open on the high side. What is your measurement, and what does the customer say?

Once again, for those just tuning in, this is yet another example of why careful review of drawings at the quotation stage (contract review) is important.

Here is the scenerio. The tolerance block on my customer's drawing is +/- .010.
The dimension in question is .460min

What is your interpretation?

What does the Customer say? I mean, we can tell you our interpretation, but in the end, isn't it about meeting the Customer's requirements? I'd love to say fix the drawing, but what does the Customer need?

I'm with Gidget. You cannot have a +/- tolerance with a minimum required dimension. I would contact the customer for clarification before accepting the order.

Does the block tolerance have the disclaimer, "Unless otherwise noted"? If it does, there's your answer--the "min" callout supersedes the block tolerance. If not, I would still say that specifying "min" without an associated "max" leaves the door open on the high side. What is your measurement, and what does the customer say?

Once again, for those just tuning in, this is yet another example of why careful review of drawings at the quotation stage (contract review) is important.

Any idea where to find a hard copy of this interpretation? My problem lies in drawing states .460 min. marked as a critical. This customer is typically "quirky" (for lack of a better term) with their drawings. Parts were made and readings reached .490-.525. All other critical dimensions were fine. Our customer received the parts, packed them into kits and then THEIR customer rejected them.....

Any idea where to find a hard copy of this interpretation? My problem lies in drawing states .460 min. marked as a critical. This customer is typically "quirky" (for lack of a better term) with their drawings. Parts were made and readings reached .490-.525. All other critical dimensions were fine. Our customer received the parts, packed them into kits and then THEIR customer rejected them.....

You didn't say whether there was an "Unless otherwise specified" disclaimer. Nonetheless, you can't logically apply a bilateral tolerance to a unilateral specification. ".460 min" allows for unlimited variation above .460. Even if this were codified somewhere--and I don't know that it is--it wouldn't make any difference unless the customer had explicitly named the controlling standard (ASME Y14.5M, for example).

This is a matter of negotiation with the customer, and in order to avoid complications you might well end up having to eat the "nonconforming" parts. This doesn't mean that the customer shouldn't be put on notice that you are making a concession in order to maintain their happiness, and that the drawing (and any others like it) need to be changed.

Here is the scenerio. The tolerance block on my customer's drawing is +/- .010.
The dimension in question is .460min

What is your interpretation?


My interpretation as an auditor is it is a conflicting dimensional statement. It is not clear. Therefore, it should have been noted during the Contract review/APQP Print review process, and resolved then. You might have had some traction to get agreement from the customer at the time.

Since you did not, there has been a glitch (almost predictable), and now you may have an issue with a customer. Now, at this juncture, you have very little traction.

Now, you still have to resolve the conflict before you move on, but you missed the opportunity to be proactive, and may have some parts to eat, as well.

This is a good real world example of why this requirement is in the standard.

This is a good real world example of why this requirement is in the standard.

What has been said is certainly true. We should also acknowledge that clarity is a requirement of purchasing as well. It was stated a couple of times here that there needs to be an up-front agreement and nobody can argue with that. Those of us on the purchasing side should take a lesson from this as well. We need to be clear about what we expect from a supplier.

That aside, why was the stated tolerance disregarded? Was there no thought to requirements of 0.470 +/- 0.010? The identification of a critical minimum requirement is, or certainly could be interpreted as, consistent with those requirements. I will be interested in what the customer actually thought they would get.

Dave

Yep. The horse [Contract Review was missing] is dead - we can stop beating it.

FYI:
Typically, my experience with job shops and contract manufacturers is that they do not take an ambiguous note or dimension as carte blanche approval to FAR EXCEED the standard tolerances for the drawing. Thus said, I would have expected most shops to have interpreted the dimension (assuming no other customer interaction during Contract Review) as 0.460 +0.020/-0.000. This means the maximum part sent to the customer would have been 0.480.

Assuming that I am understanding the situation correctly, the feature is marked only with .460 min, and the tolerance that you've referred to is what is in the drawing title block as a general tolerance (UOS). My interpretation is that the drawing would permit the feature to be no less than .460, but have no maximum.

What standard (if any) was the drawing created under? ASME Y14.5M?

Assuming that I am understanding the situation correctly, the feature is marked only with .460 min, and the tolerance that you've referred to is what is in the drawing title block as a general tolerance (UOS). My interpretation is that the drawing would permit the feature to be no less than .460, but have no maximum.

What standard (if any) was the drawing created under? ASME Y14.5M?

That is how I saw it. Tooling was actually cut to .480 (it's an extrusion).... Samples were submitted originally in 2002 and passed. Customer does not abide by any standard for creating drawings...

Yep. The horse [Contract Review was missing] is dead - we can stop beating it.

FYI:
Typically, my experience with job shops and contract manufacturers is that they do not take an ambiguous note or dimension as carte blanche approval to FAR EXCEED the standard tolerances for the drawing. Thus said, I would have expected most shops to have interpreted the dimension (assuming no other customer interaction during Contract Review) as 0.460 +0.020/-0.000. This means the maximum part sent to the customer would have been 0.480.

True, but as a job shop and contract manufacturer most of those dims are taken AS IS and treated as a reference dimension. The Min does supercede the tolerance block, the .460 min. is honored but the actual dim needs only to be close. (Close being relative to the size of the part, it's other toleranced dimensions, the caveat in the tolerance block, history with the customer and other variables.) Usually when a dimension like this considered critical by a customer it's because it is stacked against other dimensions WITH tolerances that will keep the critical dimension in control on their own. Obviously, in this instance that was not the case. Every shop has their own standard tolerance for customers that fail to provide tolerance blocks (believe it or not a standard problem on customer prints) but in this case the .460 min. is definitive. Plus, samples were already submitted and passed 5 years ago. One question though, what did those dims measure at in that inspection?
Unfortunately, that may still not save them, being right and the customer being happy don't necessarily fall under the same tree. I agree with Jim Wynne "This is a matter of negotiation with the customer, and in order to avoid complications you might well end up having to eat the "nonconforming" parts. This doesn't mean that the customer shouldn't be put on notice that you are making a concession in order to maintain their happiness, and that the drawing (and any others like it) need to be changed."

Yep. The horse [Contract Review was missing] is dead - we can stop beating it.

While there might be no sense in continuing to actually flog the decedent, it can be useful to show neophytes the corpse as evidence of what can happen if we don't try to anticipate mistakes, misunderstandings and ambiguities.

FYI:
Typically, my experience with job shops and contract manufacturers is that they do not take an ambiguous note or dimension as carte blanche approval to FAR EXCEED the standard tolerances for the drawing. Thus said, I would have expected most shops to have interpreted the dimension (assuming no other customer interaction during Contract Review) as 0.460 +0.020/-0.000. This means the maximum part sent to the customer would have been 0.480.

There is absolutely no basis for assuming that a bilateral block tolerance may be converted to a unilateral tolerance equal to the bilateral spread (or anything else) under any circumstances. In this case, the customer got what he asked for. You don't contradict your own block tolerance unintentionally. The customer assumed that some measure of restraint would be invoked, but didn't bother to define the allowable extent. Note also that the OP has stated that the customer approved the part five years ago. Like I said earlier, sometimes you have to eat some unpalatable meals in order to keep the peace, but given the evidence at hand, there's little doubt that the specification was met.

Look closer in notes on the drawing. There may be a statement that says "All dimensions +/- .010 unless specified otherwise" I would not put much stock in the +/- .010 tolerance because it sounds like a generic tolerance just placed in the title block. I would make sure the part does not go below .460 for sure and not over .470 if you are capable. It would be good to do a cpk for that feature then provide the customer with the data that corresponds to lowest scrap tolerance for you vs what they actually deem as critical specs.

I really appreciate everyone's feedback. Thankfully this is not an automotive customer (which had it been, knowing my automotive customers I don't think this would have ever happened). This customer however typically used drawings as reference believe it or not. They have since the advent of our dealings with them, gotten better.

Oh yeah - I forgot to mention... at my customer's initial contact to me upon this "rejection" they said the wall thickness was too thin. When I asked what they were measuring it to be they stated - .052 / .058. In the note section of the drawing it states: ".060 Wall (Except where noted)" - there is a section of the part that is supposed to be .040. Again, the block tolerance is all you have to fall back on and it states for an extrusion +/- .010. I told them good, then those parts are within spec. - They didn't like that response and said that we shouldn't have "assumed" the wall had a +/- .010 tolerance. In my opinion, with all that I've stated about the drawing, the drawing is clear - basic blue print reading - nothing was assumed and the drawing was taken at face value.

Oh yeah - I forgot to mention... at my customer's initial contact to me upon this "rejection" they said the wall thickness was too thin. When I asked what they were measuring it to be they stated - .052 / .058. In the note section of the drawing it states: ".060 Wall (Except where noted)" - there is a section of the part that is supposed to be .040. Again, the block tolerance is all you have to fall back on and it states for an extrusion +/- .010. I told them good, then those parts are within spec. - They didn't like that response and said that we shouldn't have "assumed" the wall had a +/- .010 tolerance. In my opinion, with all that I've stated about the drawing, the drawing is clear - basic blue print reading - nothing was assumed and the drawing was taken at face value.

Well, all I am going to add is: The customer has specified the requirements. They said it wasn't good.

This should be the ultimate answer (empasis added in bold), unless you are able to prove otherwise, using the Customer's drawing standard or something more concrete, in my opinion.

Well, all I am going to add is: The customer has specified the requirements. They said it wasn't good.

This should be the ultimate answer (empasis added in bold), unless you are able to prove otherwise, using the Customer's drawing standard or something more concrete, in my opinion.

While the ultimate answer might be giving in and making the customer happy, there comes a point when we have to assume that the customer specifications mean what they say. Customers must never be allowed to continually make suppliers pay for their mistakes. A line must be drawn somewhere, and if you keep letting them get away with it, they're likely to keep doing it. At this point, there's no telling with any of this customer's drawings whether what they're asking for is what they actually want.

While some of this can be mitigated by conscientious contract review, if there's no reason to question a specification, contract review isn't going to help. The customer isn't always right, and when they've evinced a pattern of being wrong, someone needs to put a stop to it.

While the ultimate answer might be giving in and making the customer happy, there comes a point when we have to assume that the customer specifications mean what they say. Customers must never be allowed to continually make suppliers pay for their mistakes. A line must be drawn somewhere, and if you keep letting them get away with it, they're likely to keep doing it. At this point, there's no telling with any of this customer's drawings whether what they're asking for is what they actually want.

While some of this can be mitigated by conscientious contract review, if there's no reason to question a specification, contract review isn't going to help. The customer isn't always right, and when they've evinced a pattern of being wrong, someone needs to put a stop to it.

I was not arguing that point. As you can see, I also stated that unless you can prove otherwise, using the Customer's Drawing Standard or something more concrete, how is the determination that the customer is wrong?

I have challenged numerous customers errors, but I have supported that with documentation.

While the ultimate answer might be giving in and making the customer happy, there comes a point when we have to assume that the customer specifications mean what they say. Customers must never be allowed to continually make suppliers pay for their mistakes. A line must be drawn somewhere, and if you keep letting them get away with it, they're likely to keep doing it. At this point, there's no telling with any of this customer's drawings whether what they're asking for is what they actually want.

While some of this can be mitigated by conscientious contract review, if there's no reason to question a specification, contract review isn't going to help. The customer isn't always right, and when they've evinced a pattern of being wrong, someone needs to put a stop to it.


I definitely agree with your philosophy. The customer-supplier relationship has gone out-of-kilter, and it is time the industry tries to bring some reasonable balance back to it.

However, we have to pick our battles, and in this case, I think we have agreed the supplier failed to do proper review of the drawing. So, this case might not be the right battle to apply your philosphy.

I was not arguing that point. As you can see, I also stated that unless you can prove otherwise, using the Customer's Drawing Standard or something more concrete, how is the determination that the customer is wrong?

I have challenged numerous customers errors, but I have supported that with documentation.

I'll defer to the noted quality guru Bob Dylan, who said, "You don't need to be a weatherman to know which way the wind is blowing." While it's a good thing to be aware of the standards a customer might be using with regard to engineering drawings, and qualifying new customers should always include questions about it, we generally don't require reference to standard when the customer gives an explicit specification. In the current example of wall thickness, the customer specified the required thickness without direct reference to a tolerance, in which case it's universally known (or should be) that the block tolerance is to be applied. That's why there is a tolerance block. Are you suggesting that every dimensional specification on a drawing should be questioned if it's not given a tolerance directly, or that we need a standard to tell us whether or not to apply the block tolerance?

However, we have to pick our battles, and in this case, I think we have agreed the supplier failed to do proper review of the drawing. So, this case might not be the right battle to apply your philosphy.

Sorry, but I'm not sure we have agreed that. Jim's point is that there is no reason to not trust the print the customer supplied. The correct interpretation is the one Jim outlines. The parts were supplied to the specifications called for on the drawing. Further review of the drawing wouldn't bring the problem to light.

What we have agreed is the need for understanding of the perception on both sides of the coin. This can only happen in contract negotiation or review. Both sides have to be sure they are understood before a contract is drawn. Both sides have to accept a portion of responsibility when a miscommunication occurs.

In this instance, I feel the parts were supplied to spec. Any action on the part of the supplier would be a concession for customer relations. The customer needs to look at their system of communicating purchase requirements to their suppliers. Don't be smug though supplier, you knew you were dealing with a difficult customer. Your communication may have been a bit lax too.

Another thing I agree with Jim on is that this horse will never be dead. Communication is at the root of far too many issues and nonconformity. There can never be enough discussion about the need for effective communication. Examples like this should be added to a banner page so as many people as possible will read it, add to it and learn from it.

Dave

[quote=D.Scott;200015]Sorry, but I'm not sure we have agreed that.

Actually, I was referring to Jim and I (and Wes) agreeing. See post #14 and #10.




Jim's point is that there is no reason to not trust the print the customer supplied. The correct interpretation is the one Jim outlines. The parts were supplied to the specifications called for on the drawing. Further review of the drawing wouldn't bring the problem to light.



The specs on the print contradicted themselves. That would and should be brought out in a drawing review. It was that point I thought we had pretty much agreed. Perhaps not, but the next quote seems to suggest you agreed that contract review should resolve such differences.


What we have agreed is the need for understanding of the perception on both sides of the coin. This can only happen in contract negotiation or review. Both sides have to be sure they are understood before a contract is drawn. Both sides have to accept a portion of responsibility when a miscommunication occurs.


Certainly.

In this instance, I feel the parts were supplied to spec. Any action on the part of the supplier would be a concession for customer relations.

I feel the specs almost contradict themselves, so it would be impossible to meet the spec unless the part is near nominal. These parts were clearly no where near nominal. Significantly off nominal.



The customer needs to look at their system of communicating purchase requirements to their suppliers. Don't be smug though supplier, you knew you were dealing with a difficult customer. Your communication may have been a bit lax too.

Another thing I agree with Jim on is that this horse will never be dead. Communication is at the root of far too many issues and nonconformity. There can never be enough discussion about the need for effective communication. Examples like this should be added to a banner page so as many people as possible will read it, add to it and learn from it.



Amen.

[quote]The specs on the print contradicted themselves. That would and should be brought out in a drawing review. It was that point I thought we had pretty much agreed. Perhaps not, but the next quote seems to suggest you agreed that contract review should resolve such differences.

If I understood the description of the specifications, and the OP can verify, the specifications as listed were clear cut. The dimension was .460 min. Since a minimum tolerance was applied to the specification, the title block tolerance (±.010) would not apply. QMMike, is it correct to state that there is no other tolerance applied to the individual dimension aside from "min"? It would be helpful if you can show us the area of the drawing.

In the case of wall thickness that was brought up listed as a spec of .060, since no tolerance was applied to the individual spec, the tolerance block should apply, overridden only by specific wall thickness notations, or by design requirements of specified features of the part that would change from the nominal wall thickness.

In both cases, at least to my understanding, the specifications are clear and if there is a design issue resulting from the customer not expressing what they really need, then they need to correct the issue. As a good supplier, it would be to our advantage to assist in helping them express what they need.

There is not a contradiction with these tolerances, when you have a direct tol. (.460 min) then the tolerance block does not apply. Its that simple. Those parts should be made to the .460 min call-out. There would be no reason to even question this during the quoting and contract review processes.

Somewhere I missed whether or not there had been a First Article inspection by the customer BEFORE supplier committed to manufacturing or shipping an entire order of extrusions.

Often, the very nature of extrusions gives rise to "afterthoughts" by customers when they see the First Article. At that point, even though the part may be to print, both customer and supplier can negotiate a fix without either side taking a big financial hit.

As some here have alluded, sticking too hard to a point of view may win the battle, but lose the war. Suppliers do well (except in automotive) by holding themselves out as "helpful partner and mentor" about the supplier's area of expertise about the idiosyncrasies of the manufacturing process which may not be apparent to the customer. Sorry to say, the automotive OEM can be brutal if they sense a "weakness" in a supplier.