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Machine shop responsibility to comply with "Industry Standard".
7

Machine shop responsibility to comply with "Industry Standard".

Machine shop responsibility to comply with "Industry Standard".

(OP)
I'd like to get everyones take on an issue. If a machine shop gets a print with no GD&T on it as well as no reference to any dimensioning standard, how much responsibility does a machine shop have to catch any unspecified tolerances. For example: a 3 foot long rail with various slots and holes along the length has about .020" of bow in it. Is this something a machinist should have made a special effort to avoid in the absence of any other information or should this part be considered "to print" and called good?

The kickback I'm getting from the customer is that "Industry Standard" dictates that that straightness tolerance should be the same as the tightest tolerance in the default tolerance block. I've heard this before but I thought in modern times, industry standard had fallen by the wayside since it's not documented or enforceable.

Looking forward to the feedback...

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

RE: Machine shop responsibility to comply with "Industry Standard".

If it's not on the print, explicitly or by reference, and it's not in any related contract or explicitly accepted workmanship standard, it doesn't exist.

That said, I have worked in a lot of shops where certain expectations of their suppliers had been evolved over many years of working together, and were never recorded, but were understood.  I learned of the existence of these unrecorded agreements when some idiot MBA arrived and unilaterally changed the relationship without full knowledge or understanding of the change's impact, and I got nominated to clean up the resulting mess.

This sort of thing almost always happens when said MBA changes suppliers, i.e., sends an old (and technically incomplete) print out for bids, then goes with the lowest bidder.  ... who of course does not include money or time to cover unstated requirements, and the first pieces come in 'to print, but wrong'.


Personally, I have never heard of any industry standard relating straightness or camber to any detail tolerance on the print.  Industry standards for camber with which I am acquainted typically refer to the part length, stock length, and/or some linear dimension of the section, but not to a tolerance on either.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: Machine shop responsibility to comply with "Industry Standard".

"Industry  standard" usually is "industry folklore". Standards are written, codified, and published. Anything else is popular mythology.

RE: Machine shop responsibility to comply with "Industry Standard".

"Industry Standard", "Standard Tolerances" and other such terms are used by vendors to try and get you to accept or pay for whatever piece of crap they have made.

 

RE: Machine shop responsibility to comply with "Industry Standard".

TheTick and MintJulep are right.  There's no such thing as "Industry Standard".  It's usually just codespeak for "this is the way we like to do it, so just do it this way and don't question its validity."  Most industries do have common practices, but these vary widely between industry types and even regions, or in how badly the vendor wants to get around taking responsibility for something they didn't do right.

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
Thanks for the feedback guys. It seems everyone is on the same page as I am. I just wanted to make sure my opinion wasn't the minority opinion. I still welcome any more feedback so if you're just now reading this please chime in. I realize I posted this over the weekend so I may get a lot more feedback once the workday starts.

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

RE: Machine shop responsibility to comply with "Industry Standard".

Have the customer show you the standards document where this statment comes from.   "Industry Standard" dictates that that straightness tolerance should be the same as the tightest tolerance in the default tolerance block"  Is specified.    

RE: Machine shop responsibility to comply with "Industry Standard".

I see the same issue with castings and weldment drawings specified with (2) and (3) place dimensions on drawing title blocks that show +/-.010 & +/-.030 for these. The answer is always "industry standard".
Frank

RE: Machine shop responsibility to comply with "Industry Standard".

On a couple occasions, I have felt compelled to let vendors off the hook for not complying with ambiguous drawings (meaning: "We'll pay for the bad parts").  Perhaps I am in the minority, but I believe it's my job to ask for what I need.  If I didn't do that right, I deserve what I get.

RE: Machine shop responsibility to comply with "Industry Standard".

I like to go easy on vendors when I can, because sometimes I _really_ screw up, and then need their help correcting my mistake.

However, when I draw a part straight, I don't expect it to arrive noticeably cambered.  

When it does, I'm thankful for the nitpickers on my team who provided a documented explicit chain of requirements back to, e.g. a specific industry standard for camber of straight bar stock, if not a tolerance or a note on the drawing.

Of course, after the MBAs arrive, the nitpickers are removed as unnecessary, and the survivors are pushed to take up the resulting slack, so stuff gets left off the drawings, and the shop guys start talking about the way things used to be.



 

Mike Halloran
Pembroke Pines, FL, USA

RE: Machine shop responsibility to comply with "Industry Standard".

fcsuper,

If this is a customer/account you want to keep, can you suggest a method to straighten the rails to comply with their requirementsdesires, and (having fixed their problem) then politely suggest putting a straightness requirement in a note, or (gosh what a great idea) by GD&T.

RE: Machine shop responsibility to comply with "Industry Standard".

These days "Industry Standard" means "I don't know, or use, GD&T" or "I don't know how to read drawings".

Chris
SolidWorks 10 SP5.0
ctopher's home
SolidWorks Legion

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
If I get a problem about being paid for the parts, I will probably just let it go but I won't be re-making them. This is how all the drawing are from this customer and I've brought up the lack of real specification before but as is the case with draftsmen with no GD&T knowledge, the story is always "I've never had a problem before". If a print is sent out and a vendor has to make a few phone calls to ask questions, then the parts get made twice but ultimately the guy gets what he wants, then there isn't a problem with the print. Go figure that logic.

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

RE: Machine shop responsibility to comply with "Industry Standard".

Don't just blame the little guy, from my experience the engineers, checkers and managers prefer it that way too, because they do not understand GD&T and wish it would just go away, back to the "good old days".
Frank
 

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
This is actualy the engineer but I just didn't want to make it sound like it was an engineers problem. Whoever makes the drawing--whether it's the engineer or the draftsman detailing the engineers model--should be held accountable for a drawing with ambiguous requirements.  

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

RE: Machine shop responsibility to comply with "Industry Standard".

...checkers?

"Good to know you got shoes to wear when you find the floor." - Robert Hunter
 

RE: Machine shop responsibility to comply with "Industry Standard".

My take on this pretty much matches what's been said already.  If it's not explicitly called out it's not required.  Having said that, I would hope my suppliers would question drawings I send that aren't clear rather than assuming they know what I meant.

Technically it's the engineer/designer/drafter's responsibility to provide an unambiguous drawing, but the best results occur when the manufacturer is an active part of the process, not just passively taking what drawings come their way and interpreting (or ignoring - a problem I've also seen) them in a vaccuum.
 

RE: Machine shop responsibility to comply with "Industry Standard".

The situation you indicated is pretty clearly a matter of poor documentation as others mention.

.020, unless the rail is very short, isn't a lot so to even expect the machinist to have asked for the missing info is pushing it.

Not sure exactly what industry but I've never heard that one about the smallest tol in the block tol.

If only they'd invoked 14.5 with it's rule 1, depending on the thickness tol this may have achieved what they thought they were asking for.

As to response, that comes down to how much you value this customers business by the sounds of it.

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: Machine shop responsibility to comply with "Industry Standard".

fsinfox, "Good old days?"  GD&T has been around since 1940's.  Most engineering projects in existance today happened after that.  What good old days? :) I've described it as an "irrational fear of GD&T".

And to Tick's comment, well, yeah I've paid for my mistakes too.   

Matt Lorono, CSWP
Product Definition Specialist, DS SolidWorks Corp
Personal sites:
Lorono's SolidWorks Resources & SolidWorks Legion

RE: Machine shop responsibility to comply with "Industry Standard".

Just received bunch of parts from new "less expensive" vendor.
Stuff looks like it was intentionally made as bad as our less than perfect prints will allow.
Time to talk to the boss about virtues of standards, tolerances, etc., etc., etc.,... again.
Let me join the Chorus singing "There is no such thing as "Industry Standard"".
Nowadays Craftsmanship is "what you can get away with".
sad

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
Actually, craftsmanship--as defined by old timers--is way too expensive.

 

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

RE: Machine shop responsibility to comply with "Industry Standard".

Innovation -- as defined by the Harvard Business School -- is way more expensive -- if you account for all the hidden costs -- if you can find them.

The trick is to conceal all those costs until you have cashed out.

The easiest way to conceal costs is to dispose of the people who become aware of them.

Thus endeth the lesson.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Machine shop responsibility to comply with "Industry Standard".

3
Because up till this point the discussion was rather based on opinions, I'd like to cite ISO's standpoint about this issue.

The newest edition of ISO 1101 issued in 2011 states in paragraph 5.3 "Definitive drawing principle" that:
"The drawing is definitive. All specifications shall be indicated on the drawing using GPS [GD&T] symbology (with or without specification modifiers), associated default rules or special rules and references to related documentation, e.g. regional, national or company standards. Consequently, requirements not specified on the drawing cannot be enforced."

RE: Machine shop responsibility to comply with "Industry Standard".


I gave pmarc a star.

Could somebody quote equally short, but powerful statement from ANSI/ASME?

I am preparing a memo for my boss smile
 

RE: Machine shop responsibility to comply with "Industry Standard".

ASME Y14.5M-1994 1.4 a-c gives this to some extent, though certainly without the last rather appealing sentence.  

I wonder if there'd be anything in the inspection standard, but I'm not optimistic.

I didn't see anything in 14.100 with a quick look.

Is this actually a case where even I might think Iso is more appealing than ASMEwinky smile.

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: Machine shop responsibility to comply with "Industry Standard".

...but if no spec. is invoked for the print, then how would any paragraph from any spec. apply?

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
That's a perfect point trueblood, and it's also why the whole Industry Standard discussion came up. When I said there was no specification as to which standard to inspect to, the "Industry Standard" was brought up.

I'm with you Ken; could there actually be something in ISO that I like better than ASME? Whoda thunk it?

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

RE: Machine shop responsibility to comply with "Industry Standard".

Just a short clarification. The ISO standard I was citing is 8015 not 1101. Sorry if I misled someone.

RE: Machine shop responsibility to comply with "Industry Standard".

Oh the blessings of having one standard for almost everything manufactured. ISO is not complete but most likely will be the dominant standard. Right now DIN is the most extensive and complete standard and ISO is or most likely will be a 90% copy of DIN. Right now our industry is struggling with at least five - if not more - standards. Here is a list of some:

* American Association of State & Highway Officials (AASHTO)

    * American National Standards Institute (ANSI)

    * American Society for Testing and Materials (ASTM)

    * Institute of Electrical and Electronics Engineers (IEEE)

    * National Fire Protection Association (NFPA)

    * Society of Automotive Engineers (SAE)

    * Underwriter Laboratories (UL)

We transferred the production of machines from Europe to the US, incl. all prints and found everything made to DIN. Bought a few DIN books in English and the rest was easy.     

RE: Machine shop responsibility to comply with "Industry Standard".

juergenwt,

I do not see a problem in having different standards issued by different organizations as long as the standards are complementary and do not collide one with the other.

ISO is literally one organization but actually divided to different (about 200) Technical Committees (TC) which act like different organizations but behind the facade of ISO. Not sure how DIN looks like but I suppose quite similar.

RE: Machine shop responsibility to comply with "Industry Standard".

It looks like DIN is very active "inside" of ISO as in "we have some good stuff you guys can use", but at the same time Germany is cancelling some DIN standards and directly adopting ISO as national standards.

The process is happening dynamically "as we speak". If you look thru catalogs of big suppliers like McMaster-Carr, some of their "DIN" fasteners refer to already non-existing standards and are in fact "ISO".

Similar trend can be seen everywhere as EN ("Euro Normen") and BS (British Standard) just copy ISO verbatim and adopt as national standards.
 

RE: Machine shop responsibility to comply with "Industry Standard".

There are industry standard tolerances for many casting & molding processes; I've seen the docs and used the values for rod and extrusions, rotomolding and thermoforming, and castings.  There are also industry standards for "stock" materials.  If the rail in the original example was "stock" with only modifications made to it, then those features/aspects of it which remained stock would be controlled by the industry standard.  That being said, those tolerances are generally pretty relaxed and most of the decent suppliers whom are trying to stay in business already offer significantly better than their industry standards.

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

RE: Machine shop responsibility to comply with "Industry Standard".

wish it was always the case, Kenat, but typically all I've ever seen is "2x3 alum angle stock"; sometimes just the dimensions with "STOCK" next to the number ... that's about it.  Bad detailing practices prevail.  As there are actally industry specs for alum channels, etc, that's technically all that's needed.

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

RE: Machine shop responsibility to comply with "Industry Standard".

Pretty much what I figured you'd say.

I'd argue that strictly speaking without somehow referencing the spec that controls the 'stock' sizes, that just saying 'STOCK' alone doesn't cut it as a full definition.  That's what I mean by 'complete material call out' - not just the grade but relevant standard that the bar or whatever is to.

That's what we did back in the UK for aerospace/defence stuff and I think I've seen similar for US defense etc.

That said, I'm guilty of that crime here, just saying '6061-T6' or similar and then having 'STOCK' next to a material thickness or similar.  I could try to excuse it by saying that I only do it on 'non critical' dimensions or similar but arguably it's still incomplete.

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: Machine shop responsibility to comply with "Industry Standard".

powerhound,

   Tips on Designing Cost Effective Machined Parts

   This has been linked here before.  One of the points the author makes is that he has to sell parts.  If they look crappy, or you (or your puchaser) are unhappy, he will not be making any more sales.  This imposes some discipline on the fabricator.

   On the other hand, if you specify that your part is to be fabricated as per drawing 123-456, and drawing 123-456 calls up ASME Y14.5-2009, and you call up fabricatable tolerances, there is no need for the concept of Industry Standard.   

               JHG

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
drawoh,

  Your link is really good and addresses a lot of issues that I've seen in the past, it doesn't address form at all though. I was sure hoping it would.

  I certainly agree that the fabricator should make every effort to produce a part that the customer will gladly buy. A lot of prints I've seen don't even have a surface finish callout but that doesn't necessarily mean it's okay to have a horrible, hacked up surface finish. I know the idea is to make something that the customer will want to buy again or at least provide a service that they will be willing to pay for again. It's the unspecified, yet marginal issues that I'm really asking about. I don't believe having a straightness error of .020" over 36" is unacceptable, especially when there is no indication on the print that any thought was given to tolerances. Every dimension, and I do mean EVERY DIMENSION, is a 3 place decimal which is +/-.005 in the tolerance block. This rail had holes and other features on it. Having Y14.5 specified would have automatically limited the straightness error to .010 but who's to say that would have even been too much since no thought was given to the tolerances at all?

Anyway, I think I'm on the same page as most others here. It's not as easy as saying "too bad, you should have specified it." That might be true, but it won't win me any repeat business. It's such a slippery slope...:(

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

RE: Machine shop responsibility to comply with "Industry Standard".

powerhound,

   My big experience with crappy drafting was a manufactured product.  We got to the point where there was one machine shop who knew how to make all the parts.  He responded to compaints.  He logged the phone calls.  He could make the system work.

   If he had gone out of business, it would have taken years for another shop to get up to speed.

               JHG

RE: Machine shop responsibility to comply with "Industry Standard".

"That might be true, but it won't win me any repeat business."

Probably true, powerhound.  I am lucky to have a good number of suppliers who work with me to get us what we want.  They call all the time (read to some = "annoy me") to question me about tolerances and "what we really want" vs. what the drawing says.  Sometimes we catch errors in the print, sometimes they just need clarification of how the parts work and how we measure the given feature, etc.  And when it don't fit, I take the blame when it's my fault.  That way, I can slap them silly when THEY screw up and fail to call me right away so we have a shot at salvaging the material.
 

RE: Machine shop responsibility to comply with "Industry Standard".

Have any of you also seen the note " must meet quality workmenship standards" I saw that on a print at a company i worked at and asked the engineer what he meant by that.  His response "make sure that it's done correctly even if i missed something"  I told him to remove it from the print and define the part correctly.  Needless to say I let him go a couple of months later.  

As a engineer and/or designer or the part its your responsibility to define what you need.  Suppliers are not mind readers.  In other words do your job and if you screw up admit it dont try and stick the supplier with the bill.

I can tolerate ignorance long before I can laziness. Most of the time its laziness and then its blamed on the supplier to some unknown industry standard.

As for working with the customer if they are always quick to throw the mistake on you they will cost you more money than you will make.   

RE: Machine shop responsibility to comply with "Industry Standard".

I have seen "workmanship" notes, but they harken back to the days of master machinists / master moldmakers, when they were still rather commonplace, and there was a certain quality that implicitly came with their skills.  In today's world, it's meaningless.

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

RE: Machine shop responsibility to comply with "Industry Standard".

The one "industry standard" that springs to mind but is seldom if ever seen on drawings is all sizes should be correct at 20 degrees C.

Is that taken as a given or could someone legitimately argue that the part is not undersize it is just not hot enough?
 

RE: Machine shop responsibility to comply with "Industry Standard".

(OP)
That is actually in the GD&T standard. Invoking the standard on the print definitively invokes that fundamental rule. This one can be backed up.

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

RE: Machine shop responsibility to comply with "Industry Standard".

Toddr8541,

   I send a PO to Billy Bob and Cousin Elmo's machine shop.  I want my part number 123-456 fabricated as per my drawing, coincidentally named 123-456.  My drawing states that my dimensions and tolerances are to be interepreted to ASME Y14.5M-1982.

   What does this mean?

  1. My PO is equivalent to a contract.
  2. The PO calls up my drawing 123-456, so my drawing is part of a contract.
  3. My drawing calls up ASME Y14.5M-1982, so the ASME standard is part of the contract.
   A note on my drawing stating that the work "must meet quality workmenship standards" has no meaning unless the standard is explicitly identified.  Perhaps it is my in-house standard, in which case, I have to pass a copy on to Billy Bob and Cousin Elmo, and perhaps, provide training in it.

   This is a big picture issue.  So many people out there have a "generate drawing" process.  They do not understand or care that someone out there has to order parts from the drawing, and write a meaningfuly PO.  Several others, including your inspector, have to read the drawing and interpret it correctly and consistently.   

               JHG

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