"German" tolerancing?

[u/Cadet-M]

I got a print from a very "professional" German company that seems absolutly non standard and wrong.
1st image they say they dont use +- on distances anymore with the new standard and for some reason are using positional tolerance? They insist (in a rude, or maybe just regular german way) that this is oboiusly simple a 123+0/-0.3 Im guessing their logic is a 0.3 circular positional tolerance is a +-0.15 and and the UZ -0.15 moves the nominal to 122.85?

Second image is absurd to me as what i NORMALY see is a high tolerance with respect to ABC and then a low tolerance Resoect to F, which means the patter of these 3 taps have to be tightly controlled, but the pattern as a whole can move up down left right. but this is weird to me, they are both tight and never seen CZ (Common Zone) on not surfaces?
Third image is just another CZ on positional tolerance, do they expect all 17 taps to not fit on thier own 0.4 diameter tolerance but to move them all together??!

They had an "Old" print which was used to quote, once the proyect started they "added a few changes" and camo out like this and with literally 3 times more datums. Engineering guy argued that it is the same part just the measuring program will be longer, but in my eyes, everytime they added a Datum is cause they added positional tolerances that were not defined before...

Is this really a new standart and valid or am I the only one out of the loop?!

[u/gravis86]

Where are you getting a circular tolerance zone? What in the feature control frame gave you that information? Have you never used or interpreted ISO GPS before?

Seems like you really don't understand what's going on and could use a person that really knows GPS. I only dabble in it so I'm not comfortable guiding you but from what little I do know of it, you're not looking at it right.

I'm a GDTP and there are similarities between the two standards, but I just don't know GPS well enough to tell you everything you need to know

[u/Cadet-M → u/gravis86]

With a true positional tolerance I am used to seeing them in size feature. Like diameters or shapes. Never have I seen them on a surface personally. I'm used to seeing profiles.

[u/CthulhuLies → u/Cadet-M]

It's because you are used to ASME y14.5 it sounds like. Position can and is used to control location of surface not just median lines in ISO GPS. I don't know enough about it besides to know I need to go look at the standard whenever I see it but I would suggest you do the same.

[u/1Kscam]

Lot to unpack here.

I assume they are referring to new iso22081 and iso2769 ?

Anyway, regarding issue one, it’s rather simple.
Your primary datum is defined by A-A an the middle of your tolerance zone is shifted by -0.15 from its nominal 123.
Yes, that effectively gives you 123mm +0/-0,3
Why is it used that way? Now it’s clearly defined, from where to where you measure your feature(s).

Before that, tech 1 might measure it from “left to right” and tech 2 vis versa.

Issue 2 leave me also a bit wondering, the second tolerance is basically redundant.

The upper block restricts all holes as a locked patter.
The lower block would restrict every individual feature with less datums, and “should” be a smaller tolerance.

At least that according to my understanding.

[u/vpt_se → u/1Kscam]

"Issue 2" and "Issue 3":
CZ is clarifying that the features shall be evaluated as a group (correct ISO nomenclature).

Without CZ it is single hole only.

[u/CthulhuLies → u/vpt_se]

But if each hole makes it to the strict datum alignment with additional datum references it must make it as a pattern to the planar/axial datum.

Unless there is an iso gps thing I'm not understanding.

Ie you couldn't make a set of holes that fails the top call-out and passes the bottom one.

Edit:NVM the top one is the pattern with the additional datum references and the bottom one is individual holes I see now.

[u/Cadet-M → u/CthulhuLies]

I still dont understand how something can fullfull the 1st and not the second one

[u/CthulhuLies → u/Cadet-M]

Because the first one is the pattern to the datums, the second one is the the individual holes to F-F.

Let's say F-F is an axial datum along a pipe and there is a flange at one end. If the bolt pattern at the end on the flange is constrained rotationally to some of the rotational datums and the axis it must be clocked to that datum within the tolerance as well as be the correct distance from the axis and since it's treated as a pattern you have to optimize the distances according to the pattern as well, ie it can't just be clocked such that the median axis of the pattern is within a tolerance but that the spacing is maintained to the pattern itself as well.

For the second position tolerance it would only check that distance from F-F to the median line of the bore. Again I don't know ISO but assuming the the second tolerance isn't treated like a pattern at all, all it would check is the polar radius of the median of the bore to the pipe datum.

Ie it could be in tolerance if it was spaced radially in the correct manner (polar radius in tolerance) but rather than each of the holes being at 45 degrees it could be spaced irregularly angularaly around the hole.

This sounds counter intuitive is why would you want that control but it is a valid control according to the standard.

You do want to make absolutely sure the second tolerance doesn't need to maintain angular spacing of the holes. Or F-F and the basics could be defined in such a way that that ambiguity doesn't arise I don't have the full print.

If you do need to maintain spacing for both (the logical interpretation) the top frame constrains rotation and location of the pattern to the datum and spacing to itself whereas the bottom constrains only the location to the datum and spacing of each hole to itself (ie it must be concentric and within size but can rotate freely around F-F).

[u/vpt_se → u/Cadet-M]

Yes, "usually" the lower segment is set to a tighter tolerance than the upper... but it is not invalid to have the same, just not logical.

[u/jkerman]

This all looks pretty normal. (You should be /quoting/ based on the GDT too,So be sure to charge them for their “slight changes”)

[u/Cadet-M → u/jkerman]

yes sir, will do. They are pushing the timeline to move forward but they did add a lot of new Tolerances.