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DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL
2

DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
Can someone please remind me, in ASME Y14.5 is it basically just 2.7.3 that says that just because diameters are drawn coaxial there is no coaxiality requirement implied.  To get coaxiality you need to add controls such as position, runout or concentric (I know, concentric is rarely if ever the right one depending which 'expert' you're talking too).

I get a lot of drawings of parts with 'coaxial' diameters without any controls on the coaxiality.

Do other checkers/peer reviewers etc find the same thing?

Has anyone seen any really good articles or explanations on this I could pass around.

Thanks, Ken

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

I find this to be pretty common.  If it is imperative that they be coaxial, I will suggest a runout or true position control.

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

How are the holes located? If there is a basic dimension to the c/l, then some geometrical constraint becomes necessary.
A positional tolerance is a good start, of course depending on the functionality of the features involved.

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

The largest, longest, or functionally most important coaxial feature needs to be made a datum--perhaps a 4th datum tied to the 3 main datums--and other coaxial features tied to it by position or runout.

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

  Usually coaxial features are located using a composite tolerance block as in FIG 5-51 and 5-52 in the standard. I suppose there are a few different means to achieve the same end in this case but I always stick to whatever callout is specifically for the circumstance. Start at para. 5.11 and see if any of those example gives you what you are looking for. The answer to your question is that just because features are shown coaxial, if there are no controls that tie them together, any relationship between them should not be assumed. Keep in mind that if each of the holes are located relative to identical datum reference frames and the datum features are not subject to size tolerance, then they are considered a single pattern. See para. 5.3.6.1 for a more detailed explanation.

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
Thanks all, I'll have to do a little more reading from the suggestions that powerhound gives.

Just to clarify I'm talking all coaxial features both male & female.

In fact it's most common on shafts and the like with a number of nominally coaxial diameters but no relation between the diameters.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

In most operations I've seen, it would be very hard to have multi-diameters on the same axis (and side of the part) not be co-axial simply because these normally use one op on a lathe.  In those cases, I wouldn't call out any co-axail specifications beyond what is immediately functionally required.  To call it out is a bit like saying that your mother's mother is one of two of your grandmothers.  However, there's nothing wrong with spelling it out. :)

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

If circles are drawn to look coaxial, and have center-lines drawn through the center at 90 deg, they are usually implied to be coaxial. Similar to two line drawn perpendicular, they are implied to be 90 deg.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 10-07-07)
ctopher's blog

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Chris,
  Yes, two lines shown perpendicular on a drawing can be implied 90 degrees but that's because it's a fundamental rule in the ASME standard. There is no such rule to imply coaxiality. The biggest isue you have to contend with is tolerance. Even if it was a safe practice to imply coaxiality, what would the tolerance be? With implied 90 degree rule, it's the tolerance in the tolerance block. Showing two diameters coaxial using only a centerline doesn't give a dimension so the tolerance block cannot be used.

Matt,
  You can't assume that just because features are on the same axis and on the same side of the part, that they will be done at the same time. It definitely makes more sense to do it that way but that would be like putting a tolerance of +/-.005 on a feature simply because you knew it would be made on a machine that could hold it even though +/-.5 would have been just fine. You can't assume a shop will do anything you expect that they will do. All you should count on is getting your parts made to the dimensions specified on your print.

KENAT,
  I see uncontrolled coaxial diameters all the time. It's frustrating when our QC department rejects a part in which an injector tube is welded 1mm off center yet the print says nothing about how close the injector really needed to be to the center of the burn chamber. It just shows a centerline. Rework of that sort is unnecessary when the rejection is unjustified.

  The standard says each dimension must have a tolerance except MAX, MIN, or stock dimensions. Coaxiality is no exception to this fundamental rule. Go back to what KENAT asked in the OP; 2.7.3 specifically states that features shown coaxial MUST be controlled for location or orientation. This means that you can't imply anything in this regard.

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

I agree with Chris on this one and I would use the standard tolerance shown on the drawing if there was no a feature control frame.

Dave D.
www.qmsi.ca

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)

Quote:

ASME Y14.5M-1994

2.7.3 Relationships Between Individual Features.  The limits of size do not control the orientation or location relationship between individual features.  Features shown perpendicular, coaxial, or symmetrical to each other must be controlled for location or orientation to avoid incomplete drawing requirements.

fcsuper, ctopher & dingy, I don’t see any ambiguity in what the standard says.  Showing them coaxial doesn’t imply anything and while for parts created in a single turning or boring op you’d expect pretty good coaxiality the drawing doesn’t require it from just showing them coaxial.  As such if they somehow create parts that aren’t close to coaxial, such that they aren’t fit for use, you have no comeback.

14.5 has a number of suggestions for general notes etc if perfect form at MMC is required but for a lot of the ones I see this is probably tighter than warranted by function.

I just looked at some training notes from Gary Whitmire and he has some explanation.  If anyone has any other sources that would be great.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Dave,
  If there are axes that are shown coaxial using a centerline and there is no control between the two, exactly which tolerance in the standard tolerance block would you use? The one for a three place decimal? How about a two place decimal? If you have an answer please explain the following:

 1. How did you determine which tolerance to use?
 2. What is the justification for going against what the ASME standard says?

  While it is true that there are still some GD&T concepts that are still not completely covered in the standard, this is not one of them. The correct course of action in this case is spelled out. Anything less is..."uncivilized" (who remembers that commercial?)

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Powerhound:

I agree that 5.11 explains coaxial relationship very well but sometimes it may not be reflected on a drawing. Should we (I am from the Quality background) disregard their location completely? I would not.

Let's day that I saw a drawing that did not have any relationship reflected in a FCF and one feature was "right out to lunch" Visually, it is way out of alignment. I probably would use the tolerance shown in notes section of the drawing to accept or reject the visually out of alignment feature.

If the tolerances were based on the number of digits (rather than unless otherwise noted all other tolerances are +/- **) which one would I use? Well, I would look at the number of digits on the feature and go from there.  

I did not see anything in the standard that said that if there was not a FCF on coaxial features, the coaxial features may be located anywhere. It might be there but I couldn't find it.

What section of the standard would I use? Section 1.4 (a) stating "each dimension shall have a tolerance". I would use that for a dimension of location too.

Yes I am stretching everything a bit but I am also trying to use a bit of common sense too.

I know that there are so many areas on a drawing that are not covered by examples in the standard and some that are covered in the standard cannot be confirmed properly and probably should not be in the newer standard.

Let the fun begin - comments?

 

Dave D.
www.qmsi.ca

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
You want some funwinky smile

Quote:

I did not see anything in the standard that said that if there was not a FCF on coaxial features, the coaxial features may be located anywhere. It might be there but I couldn't find it.

I would have thought 2.7.3 that I typed out in an earlier post essentially says this.

If the drawing for the visibly off part didn't have any controls on the coaxiality then yes, it is to drawing so arguably shouldn't really be rejected.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

While I am not nearly as familiar with GD&T as everybody here seems to be, I will throw my hat in anyways =)

My view would be that if all that is controlling the position is the dimension to the centerline (x & y), then both features of the same centerline will use the x & y position and the tolearance stated in the title block.

X = 2 inch
Y = 4 inch
Tol. = +/- 1/4 inch

Then one feature may be located at X=1.75, Y=3.75
and the other at X=2.25, Y=4.25

Thus, the stated allowable deviation in coaxial is:
(2*(.5^2)^.5 or approx. 0.7071 inches

I hope this adds to the conversation (I have no formal training in GD&T and we don't use it where I work, so the conversation is a little hard to follow sometimes).

-- MechEng2005

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Kenat:

Thank you.

Yes you did find something that stated it clearly but it also stated that it "must be controlled for location or orientation to avoid incomplete drawing requirements".

So now I look at a product and 1 of the coaxial features is so far out of alignment that we could consider it a cam. I could say "the drawing is a bit messed up" and accept the product. It's not my problem.

Maybe I would try and get in touch with the Designer. If the Designer said it didn't matter, the product is OK.

I have seen so many drawings with terrible application of GD&T, wrong datums, etc. Sometimes we try to figure out what the Designer wants rather than what they have on the drawing. Is that wrong?

What would you people here do if i coaxial diameter is so far out that it is a cam and there wasn't a FCF controlling the location of the features? Let it go?

Let's get some thoughts here. This is real life stuff that happens all the time on the shop floor.

Help me out here.

Dave D.
www.qmsi.ca

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Dave brings up a valuable point.  While legally a "cammed" feature may meet the drawing requirements, we have to keep in mind what the customer really needs.  To maintain a good relationship, we should strive to give the customer at least what he needs, and more where we can.  Many drawings may be vague and incomplete, but if the purpose of the part is understood we can add value to our product by meeting those needs, even when the drawing information given is lacking.
Granted, things could be much easier if everything was clearly spelled out, but this is the real world, and customer satisfaction is very important.

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

dingy2,
I definitely don't think it's wrong that you're trying to help out the designer, but I believe there is some necessity in explaining why things are incorrect.

My feeling is that the standard is pretty clear. The problem arises when the callout (or lack thereof), affects form, fit, or function. If this is the case than the part needs to be rejected, and the designer needs to be told why. If the incorrect part does not affect any of these three, then it should be dispositioned UAI. In this case, however, the designer should still be told that this is bad practice.

My .02 cents.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
"Sometimes we try to figure out what the Designer wants rather than what they have on the drawing. Is that wrong?"

There would be an argument that the machine shops etc. shouldn't have accepted the job, and certainly shouldn’t have made the part, without first asking for clarification of the drawing; or at least letting the customer know their assumptions.  Trying to guess what someone meant is fraught with potential errors.  Shops that accept ambiguous drawings and so have to do this are arguably perpetuating the problem of unclear drawings.  The designers get away with it so many times they never learn different.  

For this specific case you could perhaps cover yourselves by adding something to your standard terms stating something like “For diameters shown co-axial but with no explicit drawing requirement perfect orientation at maximum material condition with regard to related features will be assumed” however this may have a cost impact.

If the parts already made and is visibly bad I’d maybe inform the designer/customer that the part as made is eccentric to X inch, that the drawing gives no requirement for coaxiality and ask them to disposition the part.  If they say the part is scrap it would then be up to you/your organization to decide if you eat the cost in the name of customer relations or charge the customer.

I should make it clear that my OP is from the point of view of drawing checker, trying to avoid this problem in the first place by teaching the designers better and enforcing adherence to drawing conventions/standards.

In my checking role I have to try and figure out what the designers trying to say a lot, of course I can almost always easily talk to the designer but I have some feeling for the problem.  I've also had to look at old drawings for which the designer is long gone and they are often ambiguous, in this case I often have to guess just like you if I can’t determine it based on function.

I thought one of the major points of drawing standards was to avoid such ambiguities.  

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Yes, KENAT, that is the purpose of the standards.  That is why your job is so important.  My last post was addressed more to those who have no control over the drawings they have to use, but I agree with you 100% that ambiguity has no place on a proper drawing.

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
MechEng2005 For say a c'bore hole or similar that is dimensioned off a datum structure etc then I think what you put is correct.  

However for something like a shaft with multiple diameters or maybe a 'cotton reel' shape there is no dimension to the CL to apply relevant block tolerance too.  This is the kind of situation I'm more refering to.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Dave,
  When you say you would use the number of the digits on the feature to determine how far off center another coaxially shown feature could be, I hope you realize that this would be a 100% fabrication of a tolerance.
  
  The print is incomplete with no controls, so whether or not the part is passed or rejected for a coaxiality issue, it is passed or rejected based on a tolerance that doesn't exist.

vcastro66 nailed it. Whenever production workers and inspectors let things like this slide, it doesn't do anyone any good. It just allows bad drawings to stay in the system and the designers that made them just keep on making them.

I refer all to this link:

http://www.tec-ease.com/tips/sep-07.htm

This is almost what we're talking about...ambiguous prints and what happens when you don't specify EXACTLY what you want. Be sure to watch the little video clip, it has a little more information than the written tip.

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
Powerhound, awesome.  

Possibly not quite close enough to convince some of the skeptics of GD&T/standards at my employer about the coaxial diameter issue being discussed here but very useful.  I had a drawing just last week the the centerline used as a datum.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Fit and function rather than theoretical applications of GD&T - Yes, at times that concept has prevailed.

We shouldn't have to figure out the fit and function of  features since the drawing should cover the needs but many times it does not happen. Should we look at the fit and function value if a a coaxial diameter is out that far (cam) and does not have a FCF controlling its location?? Absolutely!

If I feel that there is something that could hurt its function, I would reject it, probably, on some sort of stretched tolerance application. We work as a team attempting to please the Customer and saying that Design messed up doesn't help the company. Sure, Design should be aware of the Design deficiency but what if the part was measured on the afternoon shift attempting to achieve approval so the line can start up. What would you do?

These situations happen all the time.


Dave D.
www.qmsi.ca

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

"You can't assume that just because features are on the same axis and on the same side of the part, that they will be done at the same time."

Says the standard.  I was speaking of real world.  Find me a vendor that refixtures a part on a lathe to turn one op into 2 or 3 or 4 op, and I will show a business that will not be in business for very long.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
At my previous employer we had components that due to size limitations on the machines this was sometimes done.

Specifically some diamters were milled rather than turned.

They've been in business something like 80 years and last I heard were expanding.

Pretty sure I've also seen parts that had to be turned 180 in the lathe to maching the features.  Again though this may have been a limitation of the machine/part size.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Dave,

  What the OP was asking was whether or not features shown coaxial with no controls should be considered relative to each other. The answer is a resounding NO. Are we going to comply with the standard or aren't we?
  Applying ANY tolerance to such a feature is pure guesswork, and in the absence of knowing the exact function of said feature, dangerous. Would you really pass a first article on an ambiguous dimension just to get the line going? You also have to work as a team with production, not just design.
  As far as rejecting a part on a "stretched tolerance application"; I can guarantee you that if you rejected a part that my guys built based on a tolerance that you effectively made up based on how you "felt" about a part, it would be "on like Donkey Kong" (do they say that in Canada?). I would take that situation straight up the chain and that print would get changed and the cost of the part adjusted accordingly. Oh, and production would NOT take the ding.
  I'm not discounting the importance of providing the customer with a part that will work, in spite of their jacked up print, but I am not in favor of allowing bad drawings to proliferate and arbitrarily applying whatever tolerance I saw fit. I'm trying to reconcile your statement about how you would reject a part if you felt it would hurt function. If you had no clue as to what the function was, then how would you even begin to feel that the part's function was impaired? How then would you determine a valid tolerance where none was given?

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
Dave,

Essentially if you try and impose any tolerance or similar requirement onto a drawing that isn't explicitly stated you are accepting a lot of risk.

You have to weigh the problems/costs/time etc of going back to the design authority to request clarification against the possible problems/costs/time etc of imposing incorrect assumptions.

Take a look at the link Powerhound gave earlier about the multimillion dollar costs.  Sobering!  Normally the talk of a drawing 'being a legal document' seems pretty theoretical but this would appear to be a real world example.  Should be a wake up call to everyone creating/accepting sloppy drawings.

Do we sometimes have to try and make 'a silk purse from a sows ear' sure.  However, the assumptions we make to do so, and any implications there of, should be made clear in the order/standard terms etc.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Matt,
  Take a look at the link I provided. All those diameters are shown coaxial but because of openings in interpretation left by the person that created the drawing it cost them along the lines of 8 million dollars. Axes need to be controlled, no matter what. Even though the customer put a geometric tolerance on the print, it was still ambiguous and allowed the vendor to basically pick and choose what best served their purpose.
  I understand what you're saying about real world applications and how a part will likely be set up and run, but to leave features uncontrolled just because you think they will be manufactured in a certain way thus somehow guaranteeing coaxiality by definition is a dangerous practice.
  What is the resistance to controlling these features all about? There's a way to do it, the standard clearly specifies how to do it, the fundamental rules say you have to do it, so why not just do it?

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Getting back to the original question about no coaxial requirement if there is no control, is not quite correct.

2.7.3 states "Feature shown perpendicular, coaxial, or symmetrical to each other must be controlled for location or orientation to avoid incomplete drawing requirements".

So, no controls - incomplete drawing requirement.

I gave you a hypothetical situation which caused a bit of a stir but it happens all the time and I acknowledge that I did stretch the tolerance application in this situation.

Would you believe that each and every manufacturing company have Quality Alerts floating around the shop floor? These are requirements that are not on the drawing but should have been.

Over 50% of the drawings with the application of GD&T are flawed in some manner with some of the worst ones coming from one of the big three automotive companies.

How many Designers are applying GD&T without training and don't know what the symbol means, could it be confirmed and is it the most appropriate application?

I have been training in this subject for 20 years and have seen some pretty ugly stuff out there.

Dave D.
www.qmsi.ca

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
So getting back to the point of the OP which was creating unambiguous drawings in the first place, not dealing with bad ones that have been forced upon you...

I believe the standard is pretty clear.  If you don't explicitly state some kind of coaxial requirement, there isn't one and later users of the drawing trying to impose one/tolerance of coaxiality is essentially guess work and meaningless in court.

So anyone preparing drawings that has nominally coaxial diameters should put some kind of control, even if it's loose.

If there's no control there's no requirement so strictly speaking anything is acceptable, to the point of the cam mentioned above.

I've got to admit I was a bit surprised by the level of debate on this from regular posters.  I thought the standard was clear I was just looking for more information so I can better educate the designers around here.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

"Axes need to be controlled, no matter what"...

I think even with your example, I don't by the "no matter what" portion of your statement.  It's not about being sloppy or not applying the standard.  It's about taking into account the level of detail needed to document the part desired, without getting into specifying processes.  Yes, there is more risk to not fully defining coaxial requirements because of the wording of the standard.  If 8 million dollars is on the line, then define that sucker like no tomorrow.  If it's a prototype and you are having only 1 made in a quick turn around and the part is obviously going to be done in one op on a lathe and criticallity of the diameters coxial nature is understood, then there is no value added by defining it that much, even loosely at that point.  Essentially, the part is going to be what it is and adding additional specifications bring no added value.  At times, one simply needs to find a balance.  The standard is in place to give us all a common understanding of drawings.  It isn't there to tell use how to design.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

Specifying how to control an axis is no more design than specifying how to locate a hole. You're right that the standard is to promote common understanding but I never implied that it should be used for design.

Powerhound, GDTP T-0419
Production Supervisor
Inventor 2008
Mastercam X2
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

(OP)
Fcsuper, I disagree and doubt I’ll persuade you but for what it’s worth:

If you/your employer are willing to accept the risk associated with incomplete/ambiguous drawings that's your prerogative.

I have major concerns about relying on assumptions of how parts will be made, for many reasons parts aren’t always made how the designer originally anticipated.  I’m sure the people creating the drawing that cost $8 million either didn’t know better or were happy to accept the risk or thought that it would be turned on a lathe so would be adequately concentric, I wonder if they’d reconsider that decision now.

Do you leave dimensions and/or tolerances off of drawings for one offs etc., is it not worth the effort?  That’s essentially what you’re doing by not giving any coaxiality control.

Part of my remit as checker is to minimize ambiguity on and avoid omissions from drawings.  As such I will be requiring coaxiality controls.

“The standard is in place to give us all a common understanding of drawings.  It isn't there to tell use how to design.”

And the common understanding in this case would be that showing diameters coaxial does not imply any coaxiality requirement.  As such if you show them coaxial but don’t have an explicit requirement stated, you have an incomplete drawing and no coaxiality requirement is stated or implied.  They can be way off without failing drawing requirements as there aren’t any.

I don’t see how it’s telling us how to design or what I or Powerhound said that makes you think we use it to design.

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

RE: DIAMETERS SHOWN IN LINE NOT NECESSARILY COAXIAL

I agree that it's not there to tell us how to design; however, it is there to guide the proper and correct physical representation of our design. The drawing must be COMPLETELY defined. With no coaxial constraints, it is incomplete. Simple as that.

Whether this lack of completeness affects anything is a different question altogether.

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

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