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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)





  • 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)







    I don't have a specific answer, but don't you love when you ask your customer for information and their answer is basically to figure it out your **** self?

    Sorry I'm not much help GEO
  • I think you're right, a general tolerance can't be applied to a boxed dimension.
    Maybe the customer wanted to use 2768k, for geometric dimensionning, but there's nothing about location in 2768-2...
  • I'm not so sure - I've heard talk (seen a thread) on engineers edge with something about default unspecified geometric tols.

    Sorry I can't be more specific right now, I'll try have a look at some point.
  • I left Alex Krulikowski's wonderful book at my previous employer. They paid for it after all. I think if you dig enough you will find that ISO 2768-m on the drawing automatically invokes other ISO standards, one of which is 2768k that as Jeffman and Ninjabadger mention, invokes some geometric controls as "general workmanship". I don't recall true position being one of the, more like flatness, parallelism, etc, but I am far from certain about this.

    HTH
  • I have run into this on a couple of occasions. If the customer doesn't have the "Linear Dimension Tolerances" in their title block, I use the 2798 standard. I always use the "Fine" specifications. So, if for example it is for the 0.5 MM to 3.0 MM = ±0.05 MM; The "Positional" tolerance would be 0.141 MM.
  • I don't have a specific answer, but don't you love when you ask your customer for information and their answer is basically to figure it out your **** self?

    Sorry I'm not much help GEO

    Haha you are right, that is the customers way of batting the problem straight back to you quickly with little effort on their behalf Slight smile
  • I think you're right, a general tolerance can't be applied to a boxed dimension.
    Maybe the customer wanted to use 2768k, for geometric dimensionning, but there's nothing about location in 2768-2...

    Hi JEFMAN,

    I did contemplate using K at its tighter end as the medium tolerance but like you says it doesn’t cover position Confused I might just go with that if I don’t get a better response from the customer, it sounds the most plausible option Slight smile The Link to the DIN ISO 2768 you have there in your latter post is the same one I've been using Smiley
  • I have run into this on a couple of occasions. If the customer doesn't have the "Linear Dimension Tolerances" in their title block, I use the 2798 standard. I always use the "Fine" specifications. So, if for example it is for the 0.5 MM to 3.0 MM = ±0.05 MM; The "Positional" tolerance would be 0.141 MM.

    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
  • I left Alex Krulikowski's wonderful book at my previous employer. They paid for it after all. I think if you dig enough you will find that ISO 2768-m on the drawing automatically invokes other ISO standards, one of which is 2768k that as Jeffman and Ninjabadger mention, invokes some geometric controls as "general workmanship". I don't recall true position being one of the, more like flatness, parallelism, etc, but I am far from certain about this.

    HTH

    Thanks Wes, I also can't find anything on position, I'm going to go with the tighter end of the K limit being 0.2 Slight smile

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