Is this a pattern rule or simultaneous rule 4

[sendithard]

Hope you all are doing well, happy new year.

I'm questioning my understanding on whether this is a rule for a pattern or simultaneous rule. Seen below is a bolt hole pattern, no bottom datum as this is a quick example. There is some datum shift with the A datum, I just forgot to put the symbol in the model.

Because this is a pattern, we know you get your datum shift once, meaning you cannot best fit each hole individually, the moment you find your best fit, the tolerance zones as a pattern must remain there based on the basic angle and basic bolt hole circle diam.

Is this a rule under 'simultaneous' or is this a pattern rule? I know it may not make a bit of difference, but I just want to be able to describe it correct. We have a program that is best fitting each hole independently and there was an issue today and they didn't agree with me that the holes get a one time shot at a best fit, not 5 independent best fits.

Thanks.

 

[Burunduk]

For example, in the merged standard they would have to find a consensus on topics like: default independency or Rule #1, default independency of specifications or simultaneity, default size interpretation, etc.

I would also mention quite meaningful differences in the topic of "datum reference frames"/"datum systems" and the related concepts.

 

[3DDave]

Minor vocabulary differences or actual differences in base concepts? Vocabulary differences don't count very much because those aren't symbols on the drawing; in fact the entire point is to avoid dimensioning and tolerancing vocabulary in engineering and manufacturing and inspection processes. Defaulting to independency versus the envelope principle is a problem that benefits no one.

 

[Burunduk]

Actual differences in base concepts.

 

[pmarc]

How many times, did you hear in the committee meetings when an argument is shut down just because ISO has done it?

I don't have as long history of the participation in the ASME meetings as some other folks here in this forum do, but yes I did hear about cases like that. What I have personally noticed recently though, is that some important members of the committees (e.g., in SC5 or SC5.1) start to appreciate some of the tools and concepts that have already existed in ISO GPS for a while.

I would also mention quite meaningful differences in the topic of "datum reference frames"/"datum systems" and the related concepts.

I believe the list of meaningful differences could go on. From my perspective, an important part is to make people aware that these two systems, although seemingly similar, are actually pretty different.