I am in the process of updating my activities’ in-house drawing standards and I would like to hear your opinions on the full use of employing geometric positional tolerancing.
ASME Y 14.5 allows either rectangular coordinate system or geometric positional tolerancing method.
Per ASME Y 14.5, para. 2.1.1.1 it use the term “Preferably” in regard to the use of positional tolerancing for the location of features. Some of my engineers and draftsman feel that they have a choice (which they do) whether to use rectangular coordinates dimensioning/tolerances or geometric positional tolerancing. Some feel that since geometric positional tolerancing is more “accurate” ( not me) one should only employ geometric positional tolerancing to critical features.
The way I understand geometric positional tolerancing in a nut shell is that it opens up the tolerance region ( plus the bonus tolerance) which will result in not rejecting acceptable parts when compared to the rectangular "square" tolerance zone method . With positional tolerancing, one can say that the actual center could be less “accurate” from true center ( since you have a large tolerance zone) but who cares if the part is still acceptable.
With this reasoning, I do not see why one wouldn’t want to fully employ positional tolerancing thought out all drawings.
ASME Y 14.5 allows either rectangular coordinate system or geometric positional tolerancing method.
Per ASME Y 14.5, para. 2.1.1.1 it use the term “Preferably” in regard to the use of positional tolerancing for the location of features. Some of my engineers and draftsman feel that they have a choice (which they do) whether to use rectangular coordinates dimensioning/tolerances or geometric positional tolerancing. Some feel that since geometric positional tolerancing is more “accurate” ( not me) one should only employ geometric positional tolerancing to critical features.
The way I understand geometric positional tolerancing in a nut shell is that it opens up the tolerance region ( plus the bonus tolerance) which will result in not rejecting acceptable parts when compared to the rectangular "square" tolerance zone method . With positional tolerancing, one can say that the actual center could be less “accurate” from true center ( since you have a large tolerance zone) but who cares if the part is still acceptable.
With this reasoning, I do not see why one wouldn’t want to fully employ positional tolerancing thought out all drawings.
