Understanding European Drawing Callout

Good Morning, All --

We've been having a discussion at work about the proper interpretation of a flatness specification on a French interface control drawing. The surface in question is a flat ring, roughly 1250 millimeter ID x 1300 millimeter OD; the overall flatness requirement is 0.3 millimeter (we understand that part), with a supplemental localized requirement " .03/10 ", and that's where our question is. Does the local requirement 1) mean the same as " .03 / 10x10 ", capping the planarity error of an implicit 10 millimeter x 10 millimeter square area, anywhere on the surface, 2) cap the out-of-plane profile error of any 10 millimeter long should-be-straight line on the surface, or 3) mean something else?

Thanks,

John

It should mean 0.03 mm / 10° of rotation around the ring.

Might I suggest you contact the company that issued the drawing?

After all, it's their interpretation, as determined by their QA department, that matters, not ours.

- Leigh

Leigh --

The company that issued the drawing had already provided a non-clarifying response to our question -- that the drawing complies with recognized international and ASME standards -- before I asked here.

John

with a supplemental localized requirement " .03/10 "

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That means "Not more than 0.03 mm over 10 mm".
Take any point on the surface, and within 10 mm off that point, height difference may not be more than 0.03 mm. So it is not a square of 10 * 10 mm, but a circle with 10 mm radius at any random point on that surface.


Nick

Nick's description is correct; essentially a circular zone of 10mm radius around any point on the specified plane must show no more than .03mm deviation in flatness.

What I'm wondering too is why it would even be necesssary to add any further specification to the drawing as what kind of maching is going to give "waves" on the surface?

To put my mind at rest, what is the width/height of the ring and, if you know, why would " .03 / 10x10 " even be necessary?

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It doesn't matter why it is called out that way. The customer wants it within those tolerances. That's what he pays for.

If flatness is a requirement, it is almost certain, that it either is a fitting surface or a sealing surface. They might have also specified R_a.
It also doesn't matter how you could make such a surface (badly unbalanced grinding wheel). What matters is, that a sealing/fitting surface also needs a local flatness to work.

There is no need for a drawing to specify what the draftsman has been thinking about or what he made last weekend. It specifies how the result should look like.


Nick

It's not up to the shop to question the reason for a spec.

They were not hired as engineering consultants. They were hired to make the part.

If unable to do so, they should not have bid the job in the first place.

If there's a question about a spec on the drawing, it should have been clarified with the customer before they bid it.

- Leigh

That's the stuff dictators thrive on. It might just be one of the reasons Nick gives for wanting it to be so

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No, the reason is, because I do understand what is behind the specs. At least, I can make an educated guess.
But I think any practical machinist[tm] can do that.


Nick

I question the replies so far. They go against reason! Surely the client can take the time to clarify their call-out on a print. We have assumed "professionals" (I do not count myself among them) here which have given three different interpretations to the spec'. Regardless if the print is to a standard, if there is that level of possible misinterpretation, it is worthwhile for the client to take the time to clarify. With a response by the client as outlined above... I wouldn't feel comfortable moving forward at all. Simple business---you don't need to be a machinist to understand that. A definitive answer is needed from the client so you're not screwed later. "If there's a question about a spec on the drawing, it should have been clarified with the customer before they bid it." ...in an ideal world. The spiders in the draftwork come out when you sit down to machine it. You can't tell me you haven't run into a dubious spec' after your quote---ever. I don't believe it. I-m not trying to be an argumentative troll here but a voice of sobriety in the thread. If and when they provide a definitive answer to you, John, I would appreciate to learn what it is they are/were after.

Arthur.Marks said:

I question the replies so far. They go against reason! Surely the client can take the time to clarify their call-out on a print.

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Arthur

Actually, I believe you have a point, event tough Nick's reply appears to be somewhat correct.
The OP showed .03/10, which is a callout for flatness within a unit length basis.
In this case flat within .03mm-max over 10mm-min length.
Depending on the actual symbol used, the 10mm may be:
If the "dia" symbol is used in the tolerance box, then it must be - as Nick said - within .03mm over a 10mm dia circle
If there is no "dia" symbol, then the 10mm is considered as within 2 parallel lines 10mm apart.

I cannot find any other references in my books, but I believe Tony's comment would be correct if the callout said .03/10 deg, but that would need a directional arrow showing the direction of the
tolerance band.


Now, how do I know this? Certainly not because I'm smart and all well versed.
Simply because I've made valve balls, seats and gating surfaces, where similar callouts were used and luckily I was able to ask the customer to clarify the exact meaning.
They were also nice enough to clearly indicate in the sidebar a testing method where a specific size orefice was put against the surface in question and a specific amount of vacuum had to be maintained to
qualify the function of the component.

If the "dia" symbol is used in the tolerance box, then it must be - as Nick said - within .03mm over a 10mm dia circle

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The "within .03mm over a 10mm radius circle" was meant to be a clarification, but I have to realize that it only leads to confusion. And, I wrote radius, not diameter. And that's wrong.

What is flatness tolerance?
Flatness tolerance specifies that any point on the surface to be measured lies within and including two parallel planes that are a certain distance apart.
A flatness-tolerance of 0.03 mm means, that these two planes are 0.03 mm apart. No +/-, they are simply 0.03 mm apart.
It is allowed to tilt the two parallel planes in any direction so that the points on the measured surface fit inside. There might be an other restriction that is parallelism to a given reference plane. But that wasn't the question.

Local flatness:
It specifies the distance you travel (on a straight line) and what distance the envelope is apart. Now a line doesn't define a plane, that's a contradiction. But if you add "a line in any direction", you do get a plane. But still, that doesn't define the shape of the plane, and there is no need for.
It is a bit mind banging!
Say, you travel 10 mm in the 10° direction and all points are within the envelope. And say, that there is a high point at 3 mm from the origin. And say, that right beside that point is a low point that is 0.03 mm below the start point. And say, you would find that low point when you travel in the 11° direction from the same start point. And all points along that 11° direction are within the envelope. Would that be OK? No, because any direction is allowed. So if you start point would be the high point at 3 mm in the 10° direction and you travel in the direction of the low point at 3 mm and 11°, you will see that low point and will have an envelope that is 0.06 mm apart.
NB: I left out that you are allowed to tilt the planes. That might be a fix for the described scenario.

Now from a practical POV, that is a circle with 10 mm diameter. But because of any start point is allowed and looking at the whole surface, it is shapeless.

Nick

Two quotes from Gordon in this thread:

Nick you aren't stupid but with remarks like that you're back to your old arrogant self

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That's the stuff dictators thrive on. It might just be one of the reasons Nick gives for wanting it to be so

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I'll put you on "ignore" for the time being as I've no desire to reply in kind.

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Thanks!

Nick

Gordon,

That's enough.

Nick Mueller said:

Local flatness:
It specifies the distance you travel (on a straight line) and what distance the envelope is apart. Now a line doesn't define a plane, that's a contradiction. But if you add "a line in any direction", you do get a plane. But still, that doesn't define the shape of the plane, and there is no need for.

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Nick

One of the parts I've had to make was a rotary direction valve, which was essentially a cylinder with various ports on the circumference.
Again, the callouts were quite wordy and not simply the ISO or ANSI equivalents, but basically they wanted flatness and less than X number of surface imperfections
within any .45" long radial segment on the cylinder surface.
With the cylinder being 1.5" long x 1.25 dia, in this case a .45" dia circle definition would not have been sufficient as the seal surface is through the entire length of the cylinder in one direction ( 1.5"), but
only .4 wide in the other.

I've been searching the books and notes I have as to how that would be defined within the standards, so far to no avail.
What I did find is this, with respect to the shape of tolerance zone for form, orientation, profile, runout and location:

"""
Where the specified tolerance value represents the diameter of a cylindrical zone, the diameter symbol shall be included in the feature control frame.

Where the tolerance zone is other than a diameter, the tolerance value represents the distance between two parallel straight lines or planes or the distance between two uniform boundaries.

"""

Of course, I may have compared apples to oranges using that definition....

I'm no expert on ISO tolerancing, but it looks like a waviness callout to me. Technically, the surface can do anything inside the boundaries established by size and the form tolerance (.03mm FLT?). Could look like saw teeth.

I think the .03/10 describes a reqt stating that the waviness of the surface must be such that you can't go from high to low in less than 10 degrees of arc. So something that looks like a deformed lock washer would be okay, but a serrated washer would not. This reqt probably speaks to the thickness/stiffness of the part and the ability of the assembly to restrain it.

The problem with standards is that every reader interprets them differently.

- Leigh

It's axiomatic that if you write a standard and give it to 10 people for review, you'll get 11 different interpretations, since none of theirs will agree with yours.

- Leigh

Gordon B. Clarke said:

That applies to threads started and opinions expressed in PM too Some members of course are better at misunderstanding than others.

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No. On PM if you have ten respondents to a thread you might have 30 or 40 different opinions, since they change with wind direction.

- Leigh

Good Evening, All --

A local company recently reminded all employees that they are not permitted to discuss workplace issues online, in any way. Now that a couple weeks have passed, I'll stick my head up far enough to thank all who have suggested possible interpretations of the drawing callout I asked about. I appreciate your time and interest.

John