Thru hole dimensioning in deep part 15

[Out0fSquare]

Really need help with this.

I have a cube that is eight inches square. There are four holes to be drilled through the entire depth of the part and the centerline of the holes are dimensioned only on the top view. The holes are 1/4" diameter. There is a drawing tolerance of +/- .010.

The hole pattern dimensioning uses no control boxes, neither does it have any requirement for perpendicularity, celindricity, parrellism, etc. All that is shown is the distance to the first hole from the part edges and the center-to-center location for the hole pattern.

The part was manufactured by a outside shop. Where the holes exit the part on the "bottom" they do not fall within the drawing tolerance as measured from the edges at the bottom of the cube.

I contend that the drawing does not control the exit hole locations and so our inspection department should not flag this as discrepant.

My question is this: What controls the exit hole tolerance for thru holes drilled through thick parts when the holes are dimensioned on a drawing only on the "entrance" view of the hole?

 

[bvanhiel]

OutOfSquare

Inspection assumed the holes “must” be equidistant from a certain side, top and bottom. This is NOT stated, implied or required by the drawing, any more or less than is symmetry, perpendicularity, or cylindricity. Inspection did not assume symmetry, neither did they impose perpendicularity constraints – only parallelism, and only with regard to the relationship between certain selected features, exclusive of other equally important features.

I think parallelism, and perpendicularity (not symmetry unless there was a centerline) would be implied by ANY standard. Otherwise your cube could be a 45 degree parallelogram and still be to print.

Your vendor has no defence. Even using your fantasy standard of "dimensions only apply on that face", then the print was obviously underdimensioned (no exit hole locations were given) and the vendor should have asked.

-b

 

[ewh]

... or lack of standard.
Thank you, bvanhiel.

 

[KENAT]

Outofsquare.

My stance on this is based on my very limited law training at uni and stuff I've picked up over time etc. I could be wrong, but I don't think I am.

It's common practice, perhaps even common sense to assume most of the things most others have stated that would support inspections point of view of rejecting the part.

However, how often does common sense hold up in a court of law, which is where in theory this could end up.

In the event of a dispute the drawing is a legal document and so needs to be unambiguous or there's a chance that a lawyer will find enought wiggle room to get his client off.

Outofsquare, As to your corrective action could it be something like this.

Add wording to our standard quote document that drawings which don't explicitly state a drawing standard will be assumed to generally be in accordance with ASME Y14.5M-1994. Add wording to your standard purchase order that drawings are to be assumed to be generally in accordance with ASME Y14.5M-1994 unless otherwise stated either there or on the drawing. Let the vendor know that the parts would have failed inspection to standard industry practices but as they were not explicitly invoked the part will be accepted as is. Suggest increased inspection of the vendors part on the next few orders.


KENAT, probably the least qualified checker you'll ever meet...

 

[Out0fSquare]

bvanhiel, you said, "Otherwise your cube could be a 45 degree parallelogram and still be to print."

No it couldn't, not based on the information provided above.

It was plainly stated, more than once, the cube is dimensioned on thre views -- in three dimensions. This precludes your false assumptions if you understand geometry.

You also said, "I think parallelism, and perpendicularity (not symmetry unless there was a centerline) would be implied by ANY standard." Again, do the geometry. When you enforce any geometric constraints on the part -- beyond those expressly shown -- you must make concessions, one way or the other. You don't seem to understand the geometry. Have someone draw it out for you.

Furthermore, the drawing does not show a "centerline" for the thru holes in the side views. What does that do to your, "no geometric constraint imposed absent a centerline" theory?

 

[vc66]

Actually, OutOfSquare, not to continue to beat a dead horse, but you're wrong based on your assumptions above. If you're trying to say the a point doesn't have to equal and axis and an edge doesn't have to equal a surface, then all those other dimensions on your drawing could be measuring, not from surface of one side of a cube to the other, but the dimension of the edge, and therefore as long as that infinitesimally thin line is in tolerance, the entire rest of the surface can be off kilter, and the width at the top of the cube doesn't necessarily have to match the width at the bottom of the cube. But if you dimensioned both, isn't that double dimensioning? But is it not double dimensioning as long as there is no standard to define what double dimensioning is?

I think this is more of an argument of what came first--the common sense or the standard? I'm voting for the common sense.

V

Mechanical Engineer
"When I am working on a problem, I do not think of beauty, but when I've finished, if the solution is not beautiful, I know it is wrong."

- R. Buckminster Fuller

 

[Out0fSquare]

Court cases, many times, are decided based upon whether or not a claim is reasonable to the average person (jury).

The part meets all of the dimensioned requirements of the drawing. Any reasonable person would agree. Part's good. Case closed.

 

[bvanhiel]

It was plainly stated, more than once, the cube is dimensioned on thre views -- in three dimensions. This precludes your false assumptions if you understand geometry.

You may need to retake geometry. Measuring across the flats of a parallelogram prism will give you three measurements of 8 inches just like a cube. Get someone to draw you a picture.

You also said, "I think parallelism, and perpendicularity (not symmetry unless there was a centerline) would be implied by ANY standard." Again, do the geometry. When you enforce any geometric constraints on the part -- beyond those expressly shown -- you must make concessions, one way or the other. You don't seem to understand the geometry. Have someone draw it out for you.

What concessions am I making? Show me ANY standard that does not assume parallelism and perpendicularity. Any at all.

Furthermore, the drawing does not show a "centerline" for the thru holes in the side views. What does that do to your, "no geometric constraint imposed absent a centerline" theory?

Not sure who you're quoting here, but it's pretty obvious that the holes are thru holes (they are called out as such). The centerline is not really required to communicate intent.

You're being too lax in even considering accepting these parts as being to print. It may be a bad drawing, but the part still doesn't meet the print.

-b

 

[fcsuper]

OutOfSquare, the drawing (as you described it) does not say anything close to what you are saying it says (based on your own description of the drawing and your comments here). You are making very dangerous assumptions that challenge the validity of and drawings your company makes and that of your customers too. I would suggest it creates a liability issue for your company and its customers. Ultimately, it's not about this one drawing or this one customer. It's about all the drawings and all of your customers. You gotta do what's right for your company.

Also, all of us here are offering free help to you with your question. Making accustions against us and devaluing our opinions kinda defeats the purpose of asking members of this forum for help. Take what we have given you here for what it is: advice. You are free to do with it as you please.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[ringman]

Dont think it has been answered, so again is it possible to check the part for function on the related test fixture?

 

[KENAT]

Yeah, but out of squares right ;-)

KENAT, probably the least qualified checker you'll ever meet...

 

[Out0fSquare]

I very much respect and appreciate the comments of many of the individuals here, particularly comments such as, "without the benefit of a specific standard, such as Y14.5, there is no clear cut definition of the allowables," and, "... the drawing is effectively incomplete."

That answers my question. All others are hypothetical or subjective. The part meets the drawing. Imposing other requirements necessitates subjective conjecture.

 

[Out0fSquare]

I hope to know in a few days whether the part will be accepted by my customer. If not, we're fully prepared to make whatever adjustments they requrest and will promptly do so to maintain good relations. I will post the outcome.

 

[fcsuper]

"All others are hypothetical or subjective."

Well, to be frank, I consider your general comments to be the most hypothetical and subjective out of all the opinions stated here, hince my warning above. Again, good luck.

Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group

 

[Out0fSquare]

"Measuring across the flats of a parallelogram prism will give you three measurements of 8 inches just like a cube."

I think you're describing a parallelepiped. smarty

Hope your parallelepiped doesn't have holes drilled perpendicular to the top, all the way through, 'caus when they check 'em for parallel with the sides, it won't pass. :-D

 

[Xplicator]

If I may be a voice of reason here. I have tried to weed thru all the posts and now all I have is a headache. To quote an old adage used by one of my professors - "you can't see thru the forest for your nose is against the tree!"

Please understand that there is no disrespect intended for anyone who has contributed here, this is just my two cents to best help OutofSquare and then hopefully everyone can move on to the next intriguing topic.

First the part has been manufactured right or wrong, it really doesn't matter at this point? The question is will it work for the customer purpose? Therefore, I would then submit it along with full disclosure of your findings to the customer for acceptance. If it is accepted end of issue, if not, you the contractor are responsible for making it right, because you failed to flag/reject the incomplete spec(s)(I would imagine if there is one, then there is more) prior to sending it to the sub for fab and the customer's responsible for revising their own drawing(s). This takes care of the correction of this undesirable situation.

Now on to the corporate corrective action (CAR), it would appear that there are multiple root causes here. However, you OutofSquare or your company are only responsible for your end of this undesirable situation. Which is as I already mentioned sending the incomplete/unambiguous drawing out for fab in the first place.

It is my recommendation that in the future or even immediately, have your companies procedure/process/work instruction for customer drawing review, prior to manufacturing release, revised to become a gate if you will. Then train all involved to the revised process. Include a drawing checklist form to be completed and signed, possibly using questions from the document attached. These guidelines are to be used at your own discretion, you can simply tweak to match your specific industry or company needs, this is merely a suggestion.

I hope for you and your companies sake that this is an isolated incident and that there are not anymore of their drawings that are incomplete & unambiguous. I fear that if this went to court there would be a shared liability verdict, but not necessarily 50-50. Additionally, check all the contracts/PO's, there may be some verbage about which standard is referenced, it may even be buried in a customer's corporate procurement standard which supersedes the Y14.5 standard even if listed or not on a print.

So in the end, I would chalk this up as a learning experience and again hope that it is not to painful or costly for your organization to recover from.

 

[Out0fSquare]

"you the contractor are responsible for making it right, because you failed to flag/reject the incomplete spec(s)."

Your solution is based upon a false premise. The spec is complete. The part fully meets the requirements of the drawing. No issue -- that is, until someone starts assuming that the drawing is not what the customer "really" intended, in which case, you've assumed something that isn't required by the drawing.

I'm not inclined to assume the customer doesn't know what he wants.

Should the customer not accept the part, that's called negotiation. The outcome will likely be based upon each party's overall "win-lose" assessment of their position.

 

[bvanhiel]

OutOfSquare,

Thanks for looking up the name for me. Then again a parallelepiped would still pass YOUR inspection, as you don't seem to think parallelism is implied of the holes, which was the point of bringing it up.

-b