Have you ever been rejected for a reference dimension being out of tolerance?

[larry hopperrath]

My PPAP submission dimensional report states for this dimension "Ref Dim-No Check".

 

[Jim Wynne]

My PPAP submission dimensional report states for this dimension "Ref Dim-No Check".

Was the PPAP rejected, or were parts rejected after PPAP approval? The PPAP manual specifically states that reference dimensions don't have to be measured for the PPAP dimensional report. Do you have other examples of inspections for this customer where the omission (not measuring reference dimensions) wasn't questioned?

 

[larry hopperrath]

PPAP was not rejected. We submitted several years ago. These are production parts our customer is rejecting. My customer quality contact is stating since the reference dimension is out of tolerance, the part doesnt meet the intent of the print. Our customers corporate office will be contacted shortly so they can clear any miss-understandings up. I was just curious if other people have had this happen before. I dont want this to turn into a pissing contest with the customer.
Thanks for all the input!

 

[Jim Wynne]

I dont want this to turn into a pissing contest with the customer.

I don't blame you. For the sake of others who might have similar problems, or misconceptions about reference dimensions, a few thoughts:

• On an engineering drawing, reference means reference. It means that the observer is being referred elsewhere for information concerning controlling tolerances. For example, on an assembly drawing, a dimension that's controlled at the component level might be designated "reference." It does not mean that the feature or dimension in question isn't controlled. "Reference" might also be used when (for example) an overall dimension is controlled in shorter, incremental dimensioning. In such cases, it's a good idea to verify that the sum of the incrementals is equal to the reference dimension.
• If, as a supplier, you encounter a reference dimension that can't be reconciled back to controlled dimensioning elsewhere, it's always best to question it, rather than assuming that it's insignificant.

 

[JRKH]

Certainly you don't want to compromise customer relations, but....

As a supplier you are not governed by "the intent of the drawing". You are governed by the dims and tolerances called out on the print. If all the other dims feeding into this dim are in print then your customer hasn't got a leg to stand on.

When someone comes up with this intent business I draw the line. I'm not here to read the mind of the person who drew it, or designed the system the part fits in. I just make the part as drawn.

If it's to print. Your in the clear and they can revise their drawing.

James

 

[MysterHK]

Jim's explanation is "right on the money". At my working place we have had that instance happen to us on numerous occasions.

It's always good practice to adopt a helpful attitude towards the customer. Someone should talk to your customer and convince them to eliminate the "reference" altogether at that particular dimension location and to go by the tolerance chart on the manufacturing print, if there is one. If not, one should be added in parenthesis at that dimension location (i.e., (+.005/-.000) ).

The most common ones I've seen on the tolerance charts go like this:
.xx = +/-.030, .xxx = +/-.005

Another option, which I myself prefer to see, is GD&T tolerancing.

If that doesn't work, getting a sub-component from the customer to fit test your manufactured part is another option.

Yes, some customers, you just can't seem to win and they will "knit pick" you to death. Hang in there! I feel for you.

 

[andygr]

In my experiance the use of a referance on a drawing is to provide clarity at an upper level print of a feature that is controled at a lower level.
Since it was felt that this dimension needed to be included for clarity at the upper level I would think it would be just as important to know that on the part you are reviewing that it is not actualy compliant.
I do not see that as actualy rejecting the Referance feature rather just providing the information needed to comply with the reason for using it.

 

[Phil Fields]

My customer quality contact is stating since the reference dimension is out of tolerance, the part doesnt meet the intent of the print.

Did you ask your contact what the tolerance is for this dimension?

Phil

 

[Stijloor]

Friends,

If the drawing does not state what Standard is to be utilized for its interpretation, i.e: ASME Y14.5M-1994; both parties (customer and supplier) have no legal leg to stand on. This issue is by far the most common problem with engineering drawings. Just guesswork and whomever wins the pi$$ing contest.

Stijloor.

 

[qmindiana]

No tolerances on drawing

Hi there, I was wondering if anyone has ever ran into a print that has no GD&T identified, no tolerances identified and no toelrances in the title block? Is there a standard tolerance that I should use: i.e. .x = ?mm, .xx=.?, .xxx=.?. Any help would be aprpeciated.

Thanks.