Bidirectionnal position tolerance, rectangular coordinate
Bidirectionnal position tolerance, rectangular coordinate
(OP)
Hi everyone
Is it possible to use the scheme described in figure 7-28 2009 standard without a tertiary datum? Attached is a sketch of what we are planning to do.
The hole is a locating feature and basically we only need to be really tight in one direction.
2JL
Is it possible to use the scheme described in figure 7-28 2009 standard without a tertiary datum? Attached is a sketch of what we are planning to do.
The hole is a locating feature and basically we only need to be really tight in one direction.
2JL





RE: Bidirectionnal position tolerance, rectangular coordinate
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Bidirectionnal position tolerance, rectangular coordinate
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: Bidirectionnal position tolerance, rectangular coordinate
Does it change anything if datum B was a cylindrical feature? Sorry, I should have refered to fig 7.29 with is closer to what I am looking for (and also for the crappy sketches)!
RE: Bidirectionnal position tolerance, rectangular coordinate
In this case, the pair is controlling the location and orientation from [A|B] and the perpendicularity WRT to A parallel to B.
Why wouldn't one use perpendicularity to [A|B] instead? The standard says that simultaneous requirements don't apply except to position and profile, so one could reorient a part that either passed the position tolerance or passed the perpendicularity one, but could not pass both at the same time; there is nothing in the standard that allows a designer to record his intent that they happen at the same time under these circumstances unless a note is added to the drawing.
I'm guessing the rest of the part perimeter will have some dependence on [A|B|C] or at least simultaneous with [A|B].
It's an intellectual laziness to not realize that a position tolerance controls the location of one end of a feature relative to the other end and all points in between, which is how it controls orientation. It wouldn't be so bad, but for the express exclusion of simultaneous requirements among other controls besides position and profile.
RE: Bidirectionnal position tolerance, rectangular coordinate
2JL
RE: Bidirectionnal position tolerance, rectangular coordinate
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Bidirectionnal position tolerance, rectangular coordinate
2JL
RE: Bidirectionnal position tolerance, rectangular coordinate
From Para. 4.19 you mentioned:
“In a simultaneous requirement there is no translation or rotation between the datum reference frames of the included geometric tolerances thus creating a single pattern”
So, in your interpretation, “pattern” means ”pattern of FCFs”?
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Bidirectionnal position tolerance, rectangular coordinate
RE: Bidirectionnal position tolerance, rectangular coordinate
I think you are reading what was not written, and "part requirement" applies to use of Profile.
Profile tolerance is versatile and can represent several different "part requirements", so it looks like correct choice of words for Para. 4.19
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Bidirectionnal position tolerance, rectangular coordinate
RE: Bidirectionnal position tolerance, rectangular coordinate
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: Bidirectionnal position tolerance, rectangular coordinate
They could have said - All identical DRFs are evaluated based on a single selection of datums; that is, they apply simultaneously.
Whoosh, nothing about what counts as a pattern, and without regard to type of geometric control. Just one sentence. And then a sentence that excepts those with 'SEPT REQT' noted on them.
I'd like to know they had some plan in mind, but it doesn't seem like it. It's not even useful for CMM operators or gauge makers to allow the increased mobility that applies to the standard's concept. More like someone proposed this for 1982 or earlier, and no one thought much about it. Just like TGC was taken out of 2009, but it's still in there. Sigh.
RE: Bidirectionnal position tolerance, rectangular coordinate
"SEPT REQT" excepts this.