Overriding the Envelope Requirement is ISO 1

[dlloydks]

If I have a drawing where the envelope requirement is made the default by a general note, reference to ISO 2768…-E, or other means, and I want to override the envelope requirement and have the independency principle apply to one feature of size on the drawing, how would I do that? The “I” symbol is not recognized by ISO. I was thinking I could specify a straightness tolerance with a value greater than the size tolerance, but why would that override the envelope requirement?

Any suggestions for overriding the envelope requirement in these cases? I don’t want to use notes as these drawings may be used anywhere in the world.

 

[pmarc]

dlloydks,
I already said how this can be done in the other thread.

Well, not going too much into details, there is ISO modifier that would bring Independency Principle back into play for features that do not need to be controlled by print-default Envelope Principle.

It is LP abbreviation enclosed within elongated circle. It stands for two-point measurement, so makes Independency Principle in charge again for particular feature of size if any other default principle governs the print (like Envelope Rule in your case). It was introduced in 2010 by ISO 14405-1 standard which specified tons of other modifiers that could be also used in conjuction with size dimension.

 

[dlloydks]

pmarc, so you did, sorry. Too many irons in the fire. I have a copy of ISO 14405-1. I'll study that.

 

[CheckerHater]

ISO 2768 only applies to dimensions without tolerances.

Add tolerance to your "feature of size" and you are good to go.

 

[pmarc]

CH,
Adding tolerance to a feature of size dimension will not solve the problem OP is having. If the print invokes Envelope Principle as a default condition, the tolerances itself will not bring Independency Rule into play.

 

[CheckerHater]

Well,
OP explicitly mentioned 2768 "or other means" so I tried to assure him that 2768 is the least of his problems.

To be honest my mind is blown by the idea of investing into ISO conversion, then immediately overriding fundamental ISO principles by invoking Envelope principle by default, then immediately starting to look for the way to override the override.
I guess, I got confused.

 

[pmarc]

Yeah, I agree it is not the best way to handle the problem, though not forbidden by ISO standards.

 

[CheckerHater]

Sure, blame the ISO.
For me it looks like typical Checker-speak: "Let the drawing say ISO, but everything else should stay the same".
I actually have simpler solution for that: ISO provides modifier AD in oval frame meaning something like "'Alternative Default".
Just add something like this to the title block: "Tolerancing ISO 14405 (AD) ASME 14.5-2009" and forget about ISO forever.