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True Position ISO 2768-m

GEO3D
I am currently programming a job from drawing with a hole with no true position specified, it has boxed dimensions which would imply a true position. I've notified the customer to ask what the true position would be and they said I should be able to get the true position from the ISO Spec?

To my knowledge the ISO specification used being ISO 2768-m does not specify a true position to use for boxed dimensions with no positional tolerance, this is usually illustrated on the drawing in a tolerance frame around the hole call out? I'm looking to reply with words to that effect, am I right to say this?

I've checked the standard and I can't see anything on this, any advice would be greatly appreciated Slight smile (see attached image)





  • HI Marty,

    Thank you for your input that is a great way to cover it. The pitch on the hole in question is in the over 6 up to 30 so would allow a TP of 0.565 using that method, I almost feel uncomfortable using such a high limit Astonished a great concept for using with the fine limit though.

    Thanks again Slight smile

    That is quite a high limit, but if the Customer isn't telling you what tolerance to use, they can't argue with the results...Sunglasses
  • 2768 m
    0-3mm ±0,1
    3-6mm ±0,1
    6-30mm±0,2
    30-120±0,3
    120-315±0,5

    The boxed dimensions is a target when you do your alignment.
  • Boxed dimension is usefull only to locate a tolerance zone... I believe that the customer is wrong if there's no location !!!!! Slight smile
  • I'm reviving this thread......I have a print that calls for "2768-mk" ... what would you do for true position of a central feature, like a hole centered on the part? Use the tightest K value from "symmetry?"
  • in reply to Lukas
    for concentric elements there is a general run-out tolerance in -mk of 0.2mm
  • I have looked through the 2768 versions I have and it states that the general tolerances found in 2768 does not apply to dimensions with TED (boxed dimensions) or bracketed dimensions.

    What I can understand then is that the only positional tolerance applicable is IF the feature does not have boxed dimensions and the tolerance to use is dictated by the drawing requirement (coarse, fine, medium etc) and the size of the linear dimensions leading up to your feature.

    From what I understand, if the feature have boxed dimensions, it should have a proper GD&T positional callout. 2768-2 doesn't even bother to have a position example.
  • I'm working at a company that makes extrusion mold plastic parts. Been here a year now. We have a customer that makes prints that are "busy" to put it mildly with the majority of parts not listing any tolerances. One of my jobs is to bubble the prints and create a layout document to record values for the bubbled features. To make a long story just a BIT longer, I have to dig thru to find ISO 20457:2020-03, specifically target group (TG) 5. Soooooo fun lol, especially since the ISO documents all seem to be "you must purchase to view"
  • It seems that the 2768-2 had been canceled in 2021, and replaced by ISO 22081:2021 (not very clear, as often Disappointed)
  • As far as I can see it may well be still current,

    Is ISO 2768 obsolete?




    Important things to note for the DIN ISO 2768 standard

    New international standards for general tolerances were introduced at the end of 2022. DIN ISO 22081 will soon replace the old standard DIN ISO 2768. The old standard DIN ISO 2768 is still valid (as at March 2023) and can therefore continue to be used.

    Copied and pasted from a Google search, as Jefman said, not very clear Confused





    ​
  • The old standard ISO 2768-2 (general tolerances for form and orientation) has been withdrawn and should not be used for new constructions, the ISO 2768-1 (general tolerances for linear dimensions) has not been withdrawn yet, but the use of ISO 22081 is overall recommended.

    The main purpose of ISO 22081 is to not define "random" tolerances, but to force the designer to choose meaningful general tolerances by themselves that are less prone to misunderstandings than ISO 2768. The international ISO 22081 just provides the tools to do that, but doesn't give ANY general tolerances, whereas the German suggestion DIN EN ISO 22081 provides an appendix with exemplary tolerance tables that can be referred to by the designer.

    Still, it is expected to take a number of years to catch on, so don't panic...
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