Powerhound,
Quote: “why are you providing drawings that show things that are tangent and things that are not tangent? I really don't think anyone is confused about any of it”
You did not read the thread carefully. In fact, people disagree with my definition of tangent.
Quote: “I noticed that you made no comment on the tip. I guess Don is either confused or just making things up too”
If you are talking about “EACH ELEMENT” note, it is straight from the book, together with “SEP. REQUIREMENT”, etc., etc. – nothing new. Call me when Ron promotes parallelism per unit.
You don’t like my definition of “extension of the principle”? I haven’t seen better from anyone on this forum so far.
Yes, I believe “extension of the principle” is totally made-up concept, which belongs next to “industry standard” – something to say when you have nothing to say – except profanity.
MechNorth,
You provided wonderful example; I just don’t believe the new definition that made it into 2009 was simply added because somebody decided to make-up stuff as they please; there must be some other procedure in place.
Belanger,
OK, I will try to convince you that you actually have to stick to the book.
Enter Para. 3.1: “Symbols should be used only as described herein”
To me interpretation of this paragraph is that making up your own symbology other than shown in the book is forbidden.
What to do if it’s “impossible to gather each and every tolerancing case within a ~200 pages book”?
I could be wrong, but I think 1966 version was simply saying that you can use either symbol or verbal description. Today it’s more “legalese”
Para. 3.2: “Situation may arise where the desired geometric requirement cannot be completely conveyed by symbology. In such cases, a note may be used to describe the requirement, either separately or to supplement a geometric symbol.”
So you can make-up stuff as you please, as long as you explain it on your drawing in form of a note.
In fact, I believe that by “extension of the principle” you can create your own control, say, “crookedness”, as long as you explain it on the face of the drawing “either separately or to supplement a geometric symbol”.
This is why my interpretation of the rule is: “If it’s not in the book, it is your job to explain it on the drawing”.
And this is why I strictly oppose the idea of symbology that looks “very similar” or “self-explanatory”. Nothing is self-explanatory.
I am standing by my list posted 20 Aug 12 7:32, I just didn’t have time for extensive explanation.
This forum is full of horror stories about shop “not getting” GD&T. Imagine the best possible situation: shop that invested into standard book and studying it. Your best bet will be for them to understand “by the book” examples; something not shown in the book will raise questions.
Same story with CMM – several posts mentioned CMM software not following established GD&T standards. Once again –your best bet in the perfect world is for software to match the book, not what’s left outside of it.
So if everybody will suddenly experience the need in parallelism per unit basis, let them explain on the drawing exactly what they need. Then it will probably make it into next Y14.5 – sometimes in 2025.
Hopefully I will be retired by then.